Hint: The natural gas is formed by the decomposition of the plants and animals matter with intense heat and pressure under the surface of the earth. This process takes millions of years to form natural gas.
Complete step by step answer: -Natural gas is a mixture consisting primarily of methane, including the different amount of other higher alkanes and a small amount of carbon dioxide, nitrogen, hydrogen sulphide or helium. -Natural gas is an example of non-renewable gas. -We can also say that natural gas is almost a pure methane gas which is colourless and highly flammable because the concentration of methane in natural gas is about 70% - 90%. -Whereas other molecules such as propane, butane and hexane are also present in the natural gas but a small amount. -That's why methane is considered as the major group in natural gas. -So, option B, C and D are the incorrect answer. -Moreover, other than these molecules 8 % of carbon dioxide, 0,2 % of oxygen and 5% of nitrogen is found in natural gas.
So, option A is the correct answer.
Note: Natural gas is used as a fertilizer of ethanol and generates electricity that can be used in the home and offices. Natural gas is also very beneficial because it produces less pollution and consists of fewer impurities.