Based on the vacuities, the reptiles are divided into four subclass as anapsida, parapsida, diapsida and synapsida.

When the tail is cylindrical, the snake is terrestrial and maybe poisonous or non-poisonous.
When the ventral or belly scales are small and continuous with the dorsal scales i.e., no difference between the dorsal and ventral scales, the snake is non-poisonous.
When the ventral scales are broad but do not cover the belly completely, it is a non-poisonous land snake.
So, the correct answer is option A,

When the ventral or belly scales are small and continuous with the dorsal scales i.e., no difference between the dorsal and ventral scales, the snake is non-poisonous.
When the ventral scales are broad but do not cover the belly completely, it is a non-poisonous land snake.
When the ventral or belly scales are broad and run completely across the belly, it may be a poisonous snake.
So, the correct answer is option B.

The term 'tortoise' usually refers to any land-dwelling, non-swimming chelonian. Most land-dwelling chelonians are the Testudinidae family  and the genus Testudo.
Trionyx is the soft-shelled turtle of the family Trionychidae.
Kachuga is an obsolete genus formerly used for several species of Asian turtles.
Thus, the correct answer is option B.

Chelonia is the turtle and so a reptile.
Heloderma is the only genus of its family which consists of venomous lizards.
All the three being reptiles are poikilothermic meaning, cold-blooded organisms.
So, the correct answer is option D.

A vertebra can be described in terms of the shape of the ends of the centra. Amphicoelous vertebra has centra with both ends concave and is common in fish.
The saddle-shaped articular surfaces can be traced in Heterocoelous vertebrae.
The anteriorly concave and posteriorly convex are the characteristics of Procoelous vertebrae. They are found in frogs and modern reptiles.
So, the correct answer is option D.

Sphenodon, tuatara or hatteria are all the names of the same member which is a New Zealand lizard, which, in anatomical character, differs widely from all other existing lizards. It is the only living representative of the order Rhynchocephalia, of which many mesozoic fossil species are known.
Therefore, the correct answer is option A.

Lizard belongs to class Reptilia. The marine iguana, Amblyrhynchus cristatus is an iguana found only on Galapagos islands that have the ability, unique among modern lizards, to live and forage in the sea, making it a marine reptile.
Therefore, the correct answer is option A.

Heloderma is the only venomous lizards. It can be traced in the areas like southwestern US, Mexico. They are large, stocky, slow-moving reptiles that prefer semi-arid habitats. Venom glands are located in their lower jaws, unlike snake's venom glands, which are located in their upper jaws.
So, the correct answer is option C.

A) Correct option is A

Sphenodon (tuatara) can be traced in New Zealand. It is a unique reptile. The tuatara has been dubbed a ‘living fossil’ as it is the only surviving member of an ancient group of reptiles that flourished during the time of the dinosaur. It is a medium-sized reptile and superficially resembles a lizard in appearance. It has a large head, a stout body, powerful limbs with sharp claws, and a thick tail. 

The snake's venom contains the amino-acid-oxidases which are thought to contribute to the toxicity upon envenomation. So, it is acidic in nature.
Therefore, the correct answer is option B.

Tortoise is a family Testudinidae of land-dwelling turtles in the order Testudines and genus is Testudo.
Turtles are reptiles of the order Chelonii.
Trionyx is a genus of soft shell turtles.
Tuatara are reptiles endemic to New Zealand belonging to the genus Sphenodon.
Therefore, the correct answer is option A.

The sea snakes or the coral reef snakes are venomous elapid snakes that inhabit marine environments. They all have paddle-like tails and many have laterally compressed bodies that give them eel-like appearance.
Therefore, the correct answer is option A.

Hatteria is a New Zealand lizard, which, in anatomical character, differs widely from all other existing lizards. It is the only living representative of the order Rhynchocephala, of which many mesozoic fossil species are known. It is also called Sphendon, tuatara.
Ophidia is a group of squamate reptiles including the modern snakes and all snake-like lizards. The members of Ophidia are not found in New Zealand.
So, the correct answer is option A.

The Indian krait is also called the common krait or the blue krait or Bungarus caeruleus. It is a species of venomous snake found in the jungles of Indian subcontinent.
Therefore, the correct answer is option A.

Jacobson's organ is also called as the vomeronasal organ. It is an auxiliary olfactory sense organ that is found in many animals like amphibians, reptiles, and mammals. It can be traced in reptiles and was discovered by Frederick Ruysch prior to 1732 and later by Ludwig Jacobson in 1813.
Therefore, the correct answer is option D.

A) Correct option (B) 

B) Explanation of correct option (B):

• Exoskeletal structure provides protection against the animal's body from getting external injuries. 
• Endoskeleton holds the inner components, it provides structural support to the body.
• Helps in supporting organs and helps in movement. It is the basic frame work of the body.
• The exoskeleton of tortoise consists of carapace and plastron and endoskeleton consists of an axial skeleton.
• So tortoise possess both exoskeleton and endoskeleton. 

The Squamata includes all the snakes and the lizards. They have a diapsid skull condition i.e., have two temporal fossae with loosely attached kinetic jaws.
Therefore, the correct answer is option C.

Although whales are aquatic creatures, spending all their time in the sea, they are indeed mammals because they give birth to live offspring (whereas Pisces hatch their young from eggs) and feed their young ones on milk produced by the mammary glands.
Thus, the correct answer is option D.

Flying lizards are species of lizard that move by gliding between the trees belonging to the genus Draco.
Gila monster or Heloderma is a species of venomous lizard native to the South Western Mexican state of Sonora.
The glass snake or the glass lizard are a genus, Ophisaurus of reptiles that resemble snakes.
Typhlops is a genus of blind snakes found in Europe, Africa, Asia and central and South America.
Therefore, the correct answer is option C.

When the arteries and veins lying very close to each other and form complex structure is called as a rete mirabile, found in some vertebrates. In aquatic mammals, a rete mirabile fills the swim bladder with oxygen, increasing the fish's buoyancy.
Thus, the correct answer is option D.

The longest fangs of any snake are those of the highly venomous gaboon viper.

Chameleons live on trees and bushes around the world. Some have prehensile tails that coil around the branches to maintain balance and help them climb.
So, the correct answer is option D.

The prostate gland is a walnut-sized gland located between the bladder and the penis in mammals
Pineal gland is a small endocrine gland present in the brain in mammals.
Cowper's gland is a pair of exocrine glands in the male reproductive system.
On the other hand, the conglobate gland is the gland present in the male cockroaches and is a reproductive organ.
Thus, the correct answer is option C.

The hippopotamus is a large, herbivorous mammal. And it can stay partially submerged in water as well as on land and so is amphibious. They can spend about 16 hours per day in water.
Thus, the correct answer is option A.

The beaver, belonging to the genus Castor and are semi-aquatic rodents. They exhibit nocturnal behavior. They found in North America and South America.
Thus, the correct answer is option C.

All reptiles have a three-chambered heart (except for a crocodile) consisting of two atria and one ventricle. While monotreme, being mammal, have a four-chambered heart. The body of reptiles is covered by scales while that of mammals is covered by hair.
Thus, the correct answer is option A.

A diastema is a natural space or gap between two teeth. It appears most often between the two upper front teeth, however, gaps can occur between any two teeth. In rabbits, there is a space where teeth are present between the incisors and the cheek teeth.
Thus, the correct answer is option C.

Cetaceans or whales, dolphins possess all the mammalian characters except body hairs. It is the largest group of hairless mammals because hair doesn't give them aquatic lifestyles. They have opted to insulate themselves with a thick layer of blubber.
Therefore, the correct answer is option D.

Horse, Rhino and Tapirus all are mammals which are odd-toed ungulates and they compose the order Perissodactyla.
Deer is an even-toed ungulate belonging to the order Artiodactyla.
Thus, the correct answer is option D.

True flying lemurs belong to order dermoptera. They can not fly but glide with help of patagium which is a hairy fold of skin extending from neck to tail like a parachute. They are nocturnal and arboreal organisms and feed on leaves and fruits. Correct answer is D.

The testicles of elephants are located within the body, close to the kidneys, intra-abdominal because its internal body temperature is optimum for sperm production.
Thus, the correct answer is option A.

The Indian ass is Equus hemionus khur, subspecies of the Onager native to Southern Asia.
Thus, the correct answer is option B.

Echidna also known as 'spiny anteaters', belong to the family Tachyglossidae in the Monotreme order of egg-laying mammals. Its body is covered with hair and spines. They have a tiny mouth and toothless jaws. It gives birth to 4 young ones at a time and of the same sex. Hence, option B is correct.

Metatherians are a group of animals that includes all mammals more closely related to marsupials than to placentals and found in Australia. 
Fossorial are those animals that are adapted to digging and live underground, such as naked mole rat. 
Flying foxes are megabats and they belong to order Chiroptera. 
Elephant, which comes under order Proboscidea, are distinguished by tusks and long, muscular trunks. They are largest land animals. 
Animals including humans have a menstrual cycle or estrous cycle in the females counterparts. It happened every month whereby females get ready for pregnancy. 
Lagomorphs belongs to order Lagomorpha having tow living families one of which is Leporidae, rabbits belong to this. Rabbits have four incisors in the upper jaw with open root canals. 
Prototherians are egg laying mammals belongs to sub class Monotremata, therefore they share features with primitive vertebrates. Thus, the correct answer is option A.

Therapsida is a group of synapsids and characterized by the presence of four limbs extend vertically beneath the body, as opposed to the sprawling posture of other reptiles. It includes mammals and their ancestors.

Killer whale or Orcinus orca is a toothed whale belonging to the oceanic dolphin family. 
Blue whale or Balaenoptera musculus is a marine mammal belonging to the baleen whales. 
Hump back whale or Megaptera noveeangliae is a species of baleen whale. 
Pigmy whale or Caperea marginata is a member or cetotheres, a family of baleen whales. Thus, the correct answer is option B.

Didelphis, commonly known as large American opossums belong to the order Didelphimorphia. It is the omnivorous species of class Mammalia and is characterized by the presence of prehensile tails and the tendency to "play possum" (feign dead) when cornered. 

A hedgehog is also called as Erinaceous. It is any of the spiny mammals of the subfamily Erinaceinae, which is in the order Erinaceomorpha. They found in Africa, Asia and Europe.
Thus, the correct answer is A.

Balaenoptera musculus is the name of the blue whale. It is the largest marine mammal. The largest population  of this mammal is found in Antarctic ocean. It is 30 meter long with 173 tonnes weight. They have long body which is tapering at both the ends. The head is flat and dorsal fin is short. They have flippers. The lung capacity is very high. 
Thus, the correct answer is option B.

Monotremes are the egg-laying mammal with the unique property that they have only a single passage or opening i.e., the cloaca, for both excretion and reproduction. 

Pinnipeds, colloquially known as seals are semiaquatic marine mammals belonging to the order Carnivora and clade are Pinnipedia. It is characterized by the fin foot and includes fur seal, elephant seal, sea lion, walrus.

Protoglossus is the genus in Hemichordata. Oryctolagus also called as European rabbit which is the mammal as they possess mammary gland, placenta and other mammalian characters. Tachyglossus is the short-beaked echidna, egg laying mammal and thus do not possess placenta. Sacchaglossus is a genus of acorn worm.
Thus, the correct answer is option B.

Baleen is a filter-feeder system inside the mouth of baleen whales. It works when a whale opens its mouth underwater and the whale takes in water baleen filters the food from water and then pushes the water out. 

The cow belongs to the order Artiodactyl called as a cloven-hoofed mammal or even-toed ungulates. 
The order Perissodactyla includes rhino, tapers, horses and zebras and are odd-toed ungulates. 
The order Cetacea includes the marine mammals like whales, dolphins and porpoises.
The Proboscidea are an order of eutherian mammals that include the living elephants as well as extinct mammoths. Thus, the correct answer is option A.