Choose the incorrect statement.

• A
  We are encouraged to plant more trees so as to ensure a clean environment and also provide biomass fuel.
• B
  Gobar-gas is produced when crops,vegetable wastes,etc.,decompose in the absence of oxygen.
• C
  The main ingredient of biogas is ethane and it gives a lot of smoke and also produces a lot of residual ash.
• D
  Biomass is a renewable source of energy.