[A] : Ozone depletion at the south pole will threats world's fisheries .
[R] : Ozone depletion will kill phytoplankton , the food of fishes .

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false