In the Equation for Net Primary Production, Would You Ever

Multiple Choice

In the equation for net primary production, would you ever expect R to be zero?

A) Yes, but only when the system is at equilibrium.
B) Yes, but only when the system is out of equilibrium.
C) No, unless the system is at equilibrium.
D) No, unless the system is out of equilibrium
E) No, because there would be no life if R was zero.