The hottest region of Bunsen flame shown in the figure is region $$2$$. It is just above the tip of the primary flame. It reaches about 1,500 °C (2,700 °F).

Nitrogen Oxides are emitted in car exhaust and are a cause of acid rain.
Fuels, such as coal and petroleum have some amount of sulphur and nitrogen. On combustion, such fuels form oxides of sulphur and nitrogen which is an environmental hazard and cause of acid rain.

Atmospheric air contain oxygen which is necessary for combustion because complete oxidation is called combustion. Hence, assertion is incorrect but reason is correct.

The correct answer is A.

Water cannot be used as a fire extinguisher for fires involving petrol, kerosene or diesel. That's because these substances are lighter than water and so, they float on it and continue burning. Moreover, the water will carry these inflammable substances further, and so, it spreads the fire even more. For such fires, carbon dioxide is a suitable option as it covers the inflammable substances and cuts off the oxygen supply.

A good fuel should have high calorific value, should be cheap, should not cause any pollution and should be easy to transport.

Water cools the combustible material so that its temperature is brought below the ignition temperature. This prevents the fire from spreading. Water vapour also surrounded the combustible material helping in cutting off the supply of air. So, the fire is extinguished.

The substance that burns in the presence of oxygen and heat are called combustible substances whereas that do not burn are non-combustible substances. Elements such as carbon, hydrogen and sulphur present in the fuel makes it combustible.

The flame consist of three zones: 

Three things are required in proper combination before ignition and combustion can take place---heat, oxygen, and fuel. oxygen helps as an oxidizer in the oxidizing hydrocarbons to form $$CO_2, H_2O $$ and heat.

The most common fire extinguisher is water, but water works only when things like wood and paper are on fire. 

Geothermal energy is the energy obtained from the heat of hot dry rocks in the earth's crust, geysers, hot springs, etc.

For fires involving electrical equipment and inflammable material like petrol, carbon dioxide is the best extinguisher. Carbon dioxide being heavier than oxygen covers the fire like a blanket. Since the contact between the fuel/inflammable material and oxygen is cut off, the fire is extinguished.

Carbon dioxide is a gas that can be store in cylinders under high pressure like LPG. When it is released from the cylinder, carbon dioxide expands enormously in volume and cools down. So, it does not only forms a blanket around the fire but also brings down the temperature of the fuel.

The unit of calorific value is kJ/kg or J/kg. The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value

The cooking gas burns rapidly and produces heat and light. Such combustion is called rapid combustion. The burning of the matchstick is also an example of rapid combustion.

The cooking gas burns rapidly and produces heat and light. Such combustion is called rapid combustion. The burning of matchsticks is also an example of rapid combustion. Ignition of cracker and burning of Phosphorous is an example of Explosion.

Ignition of a cracker is an example of explosion. When a cracker is ignited, large amount of heat, light, gas and sound are released due to a sudden reaction. 

An explosion can take place when pressure is applied on the cracker. When a cracker is ignited, a large amount of heat, light, gas, and sound are released due to a sudden reaction that creates pressure inside. 

When fuel is added to exhaust gases in a jet, engine combustion takes place to release energy so that it gives additional thrust to increase efficiency of the engine.

It's not a physical process rather it's a chemical process.

Sodium bicarbonate can be used for fire extinguishers purpose as it releases carbon dioxide. 

$$C_4H_{10} +\dfrac{9}{2} O_2 \rightarrow 4CO(g) +5H_2O (l)$$

The outermost portion is blue.

The minimum temperature at which a substance starts to burn is called its ignition temperature. Different fuels have different ignition temperatures. For combustion, ignition temperature should at least be achieved. Substance starts burning only at a temperature equal to ignition temperature or more than it.

The total energy released as heat when a substance undergoes complete combustion with oxygen for a specific quantity is the calorific value. It is a measure of fuel efficiency. It is measured in kilojoule per kilogram ($$kJ/kg$$).