E. Answer the following questions in one word or a single sentence. 1. What is a fuel?
2. Name the type of coal which contains minimum carbon content.
3. Define carbonisation.
4. Which gas is also known as the town gas?
5. What is the black gold?
6. Name the constituents of petroleum used to make road surfaces.

Source : The web and textbooks

A fuel is any material such as coal, gas, or oil that is burned to produce heat or power.Lignite: Lignite coal, (brown coal,) is the lowest grade coal with the least concentration of carbonCarbonization is the conversion of organic matters like plants and dead animal remains into carbon through destructive distillation. Coal gas :Town gas Also known as coal gas, and contains hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), nitrogen (N2) and volatile hydrocarbons. It is made by blowing air and steam over an incandescent fuel bed, usually of coke or coal.Black gold = oilBitumen is the petroleum product which is used for surfacing of roads and paints these days

Explanation:

Positive feedback occurs to increase the change or output: the result of a reaction is amplified to make it occur more quickly. Negative feedback occurs to reduce the change or output: the result of a reaction is reduced to bring the system back to a stable state.