Explanation:

Let’s look at each statement:

- Option 1: "It is environmentally much cleaner than the other fossil fuels."

This is true. CNG emits fewer pollutants like CO2, CO, and NOx than petrol, diesel, or coal.

- Option 2: "It is obtained during refining of crude oil."

This is not true. CNG is mostly obtained from natural gas wells or oil wells but not primarily during the refining of crude oil.

- Option 3: "It comprises primarily methane."

This is correct. Methane (CH4) is the major component.

- Option 4: "Unlike LPG, it is not liquefied."

Correct. CNG is stored as a compressed gas, not a liquid like LPG.

So, the statement that is NOT TRUE is Option 2.