Choose the correct alternative which will improve the

Solution

were prepared is grammatically incorrect. Were is in simple past tense but in the sentence ,past perfect tense must be used because when two events occur in the past with one event preceding the other ,the first even takes the past perfect tense form of the verb and the second event takes the simple past tense. Have prepare is wrong because with perfect tense we use the past participle of the verb and also have is used in the perfect perfect tense.So had prepared is the correct sentence.