The correct option is B donated
A tense is a form of a verb which provides derails about the action (timing, progress, completion, etc.). Option B)donated is correct as the principal clause uses the simple past tense (had) and therefore, past perfect, simple past, or simple present can be used in the subordinate clause. Here, would have donated is used as it expresses a condition. The other options are wrong as no other tense can be used in the subordinate clause. The correct answer is B)donated.