(A) may
(B) can
(C) could
(D) would
Correct!
When the verb in the main clause is in the past tense, we use a past tense in the subordinate clause. Could is the past tense of can.
(A) may
(B) can
(C) could
(D) would
When the verb in the main clause is in the past tense, we use a past tense in the subordinate clause. Could is the past tense of can.