What is the rate at which solar energy is converted and stored by the producers per unit area over a time period called?

What is the rate at which solar energy is converted and stored by the

1.	What is the rate at which solar energy is converted and stored by the producers per unit area over a time period called?
A.	Primary productivity
B.	Tertiary productivity
C.	Gross primary productivity
D.	Net productivity
Answer» C. Gross primary productivity