The correct options are
A Natural gas is an important fossil fuel as it is easy to transport through pipes.
C CNG is used for power generation.
D CNG is used as fuel in vehicles.
The statements (A), (C) and (D) are true. Natural gas is an important fossil fuel as it is easy to transport through pipes. Natural gas is stored under high pressure as compressed natural gas (CNG). CNG is used for power generation. CNG is used as fuel for transport vehicles as it is less polluting. It is a cleaner fuel.