Question

We ___________ apologised if we had been at fault. *​

Answer 1

Answer:

Would have is the correct answer of your Question

Answer 2

Answer:

We would have apologized if we had been at fault. Correct answer is would have.

Explanation:

Would have is the past form of the tense Will have. Normally, would have is used before past participle i.e., would have + past participle. Would is used to show the possibility of something that is done in the past. As in above sentence, there is condition in correspondence to the past that if a person was at fault, he/she would have apologized. Hence, would have is the correct answer.