Anaerobic fermentation is a process which helps in the formation of:
A.coal gas
B.natural gas
C.water gas
D.Petroleum

Hint: Fermentation refers to the metabolic process by which organic molecules (mainly glucose) are converted into acids, gases or alcohol within the absence of oxygen or any electron transport chain. Anaerobic respiration is a type of respiration where oxygen is not used; instead, organic or inorganic molecules are used as final electron acceptors.

Complete step by step answer:
Fermentation is a metabolic process. It causes a chemical change in organic substances with the assistance of enzymes. Moreover, it is a process where organisms convert carbohydrates into acid or alcohol.
Common Fermentation Examples Are –
Yeast performing fermentation to get energy and during this process, converting sugar into alcohol. This is often a really common phenomenon which will be observed often.
Bacteria use this process to convert carbohydrates into lactic acid.
People use these organisms to form yogurt, bread, wine, and biofuels. The basic mechanism for fermentation remains present in all cells of higher organisms as well. Mammalian muscle carries out fermentation during periods of intense exercise where oxygen supply becomes limited, leading to the creation of lactic acid.
Natural gas is made by the action of anaerobic bacteria on the plants or vegetation thousands of years ago. Over the years under high temperature and pressure, methane gets converted to natural gas.

Hence, the right answer is Option B.

Note:
Natural gas is made by the action of anaerobic bacteria on the plants or vegetation thousands of years ago. Over the years under high temperature and pressure, methane gets converted to natural gas. Aerobic processes are processes that need the presence of oxygen like in aerobic respiration for producing energy whereas in, the anaerobic process happens without oxygen like in muscle fatigue where glucose breaks down to produce energy without oxygen.