大全-01-24

24.   Even though its per capita food supply hardly increased during two decades, stringent rationing and planned distribution have allowed the People’s Republic of China to ensure nutritional levels of 2,000 calories per person per day for its population.

(A) Even though its per capita food supply hardly increased during

(B) Even though its per capita food supply has hardly increased in

(C) Despite its per capita food supply hardly increasing over

(D) Despite there being hardly any increase in its per capita food supply during（B）

(E) Although there is hardly any increase in per capita food supply for

The answer is B. Why not A? Why we have to use present perfect tense here?

Well, thanks!

Or maybe we should use present perfect tense because of "have allowed"?