Which of the following statements about the greenhouse effect is false?

A) Without the greenhouse effect, the atmosphere might be too cold for current life forms.
B) CO₂ concentrations in the atmosphere started increasing during the Industrial Revolution.
C) Methane is an important greenhouse and has several natural sources.
D) The impact of water vapor and clouds on global warming is difficult to quantify.
E) CFCs are a natural greenhouse gas with high warming potential.