Flame color determines the rate of combustion and thus the temperature difference producing a different color flame. In LPG the blue zone is the zone of complete combustion of fuel. So, the amount of soot decreases, and the temperature is highest as high heat is released.

Fossil fuels were formed from the buried remains of plants and tiny animals that lived hundereds of millions of years ago. Coal, petroleum, natural gas and propane all are formed by same process and hence known as fossil fuels.

Lighting of an electric lamp cannot be described as combustion. During the lighting of an electric lamp, the electrical energy is converted into light energy. However, during combustion, chemical energy is converted into thermal energy.

The carbohydrate is glucose. The combustion of glucose is as follows:

A blue colored flame which produces very little light is called non-luminous flame. In other words when a fuel undergoes complete combustion it is non luminous flame.

This happens because oxygen in the air inside the glass tumbler is utilized in burning the candle. All the oxygen gets converted into carbon dioxide. Carbon dioxide does not support burning and hence candles stop burning.

Oxygen is a supporter of combustion. In its absence, the oil cannot burn. So, holes are provided at the bottom of the lamp to ensure a continuous supply of oxygen to allow the oil to burn.

Ideal fuel shows the following characteristics:

• It should be inexpensive,
• It should have a low ignition temperature
• It should be easily available,
• It should produce a large amount of heat,
• It can be easily transported.
• It has a high calorific value.
• It should burns easily in the air at a moderate rate.

Hence option D is correct.

Here are the calorific values of the given fuels: 

The hottest part of the flame is the outer zone with blue color which has the highest temperature due to complete combustion, the yellow part of the flame has a temperature less than the outer part.

Hydrogen is very combustible because it is very reactive. It can easily combine with an oxidizer to be oxidized. In fact, hydrogen can be oxidized or reduced and can combine with every element except noble gases.

Oxygen gas supports the combustion of fuels. For example, cooking gas and producer gas are fuels that burn in the presence of oxygen gas. They will not burn in its absence. Nitrogen is a non-flammable gas.

Quality that is not suitable for fuel is carbon particles are expelled with smoke and cause air pollution.

The lowest temperature at which a combustible substance when heated takes fire in the air and continues to burn also called autogenous ignition temperature.

Metamorphic rocks such as marble are formed by tremendous heat and pressure and fossils can not be found in such places. They are usually found in Sedimentary rocks as these rocks have formed at low temperatures and pressure and suitable for fossils.

Some Class-B fires (hydrocarbons, petroleums, and fuels on fire) cannot be efficiently controlled with water. $$CO_2$$ being heavier than oxygen covers the fire like a blanket. Hence, one of the important factor for fire is cut off and the fire is controlled.

Nitrogen gas is not highly reactive i.e does not support combustion with other molecules in the atmosphere and is mainly present in the air as $$N_2$$ ($$78 \%$$). Unreactive behavior results from the powerful triple bonds that form between the three pairs of electrons shared between two nitrogen atoms. These bonds have relatively short radii, which requires more energy to break. Nitrogen becomes more reactive at higher temperatures.  One common nitrogen-based reaction that occurs in the atmosphere is the formation of nitrogen oxide ($$NO$$), during storms when lightning strikes.

True.

Ideal fuel has high calorific value. This ensures that more amount of heat energy is released from the combustion of unit mass of fuel. In other words, a fuel with high calorific value is better than a fuel having low calorific value.

Carbon dioxide is used in fire extinguisher, the release of gas under pressure has a cooling effect.

$$Na_2CO_3 + H_2SO_4 \rightarrow  Na_2SO_4 + H_2O + CO_2$$In the inner part of the extinguisher, the whole container is filled with the strong solution of sodium carbonate and there is a glass tube in the bottom of the container contains sulfuric acid. The glass tube is broken with a powerful pressure when required. And the solutions are reacted with each other and carbon dioxide is produced. Then the $$CO_2$$ is released through the tiny hole in a very high pressure and extinguishes the fire.

Carbon dioxide is neither combustible nor a supporter of combustion, as $$CO_2$$  is an oxide of carbon a stable bonding of one carbon atom with $$2$$ oxygen atoms i.e it is already oxidized. in fact, it is used as a fire extinguisher.

Kerosene oil has lower ignition temperature is highly flammable and easily catches fire very quickly.

Oxygen supports combustion and is used up in burning. When oxygen combines, chemically, with another chemical like carbon or hydrogen, energy is released rapidly(in the form of heat) which can create fire.

Charcoal burns in air mainly to produce $$CO_2$$. It usually burns slowly giving an orange glow from the burning layer of charcoal and leaving white ash behind.

A candle burns in a jar of oxygen as it is a supporter of combustion i.e hydrocarbons in the presence of oxygen produce carbon dioxide, water, and heat,  but is extinguished in nitrogen, as it does not support combustion due to its triple bond.