(a) The correct answer is ……...Coal, petroleum and ……...natural gas.

Coal, Petroleum and natural gas are formed from the dead remains of living organisms or fossils. So, these are all known as fossil fuels.

(b) The correct answer is ………... carbon.

Coal is formed from the remains of vegetation, it is also called a fossil fuel. Being produced from vegetation it mainly contains carbon.

(c) The correct answer is …. Carbonisation.

Carbonisation is the process by which plant material or vegetation buried deep under the earth was slowly converted into coal. Since, coal was formed from the remains of vegetation, it is also known as fossil fuel.

(d) The correct answer is ……refining.

Petroleum is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc. The process of separating the various constituents or fractions of petroleum is known as refining. It is carried out in a petroleum refinery.

(e) The correct answer is ……CNG.

The full form of CNG is compressed natural gas. Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG).

(f) The correct answer is ……. pollution; warming.

Burning of fossil fuels affects the environment because they release carbon dioxide and other harmful gases such as Sulphur dioxide, nitrogen oxides and carbon monoxides. These gases trap heat in the earth’s atmosphere and causes global warming which contributes to global climate change.