A. would be
B. have been
C. are
D. had been

Correct Answer:

Option D – had been

Explanation

The correct answer is ‘D’ because it is a past perfect tense. Option ‘A’ is ‘would be’ which implies the future past tense, option ‘B’ ‘have been’ which means/is a present perfect tense, option ‘C’ are which indicates ‘plural’

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