Here's a problem to solve: Which statement best explains why wood is considered a renewable energy resource and coal is not?

Among the 4 following options, which is the correct answer?

- A: Wood is easier to find than coal.
 
- B: Wood has less carbon per unit mass than coal.
 
- C: Wood grows more quickly than coal forms.
 
- D: Wood has less stored energy per unit mass than coal.
 