Wood is easier to find than coal. Wood has less carbon per unit mass than coal. Wood grows more quickly than coal forms. Wood has less stored energy per unit mass than coal.
I gave my students this multiple choice question: Which statement best explains why wood is considered a renewable energy resource and coal is not?

Only one answer is correct among these 4 choices:
- Wood is easier to find than coal.
- Wood has less carbon per unit mass than coal.
- Wood grows more quickly than coal forms.
- Wood has less stored energy per unit mass than coal.

Could you tell me which one is correct?

Wood grows more quickly than coal forms.