What is the best summary of paragraph 6, which talks about harmful emissions?

A
According to environmentalists, one regular car emits more harmful carbon dioxide gas than three hybrid cars combined.

B
While burning fossil fuels creates gases that are very harmful to the planet, hybrids can reduce production of those gases.

C
Harmful greenhouse gases, like carbon dioxide, are known to accumulate in the atmosphere and trap heat from the sun.

D
Fossil fuels are not renewable, which means that once they've been burned up, they're gone for good.​