Answer: B) PAST PERFECT.
Explanation for this question is being written.
Answer: A) Had done.
Answer: A) Had
Answer: D) Had talked.
Answer: C) Had closed.
Answer: B) Had written.
Answer: A) Had written.
Answer: B) Had changed.
Answer: A) Had seen.
Answer: A) Had built.
Answer: A) Had already started.
Answer: B) Past perfect.
Answer: A) Had explained.
Answer: A) Had been.
Answer: B) Had borrowed.
Answer: A) Past perfect.
Answer: A) Past
Answer: B) Had come.
Answer: A) Had planted.
Answer: A) Had gone.
Answer: B) Past Perfect.
Answer: A) Had graduated.
Answer: C) Had
Answer: B) Had all gone.
Answer: B) Had never used.
Answer: D) They had left before the rain started.
Answer: C) Left
Answer: D) Had read.
Answer: A) She had been working here for five years.
Answer: B) Had / tried.
Answer: B) Had told.
Answer: B) Had set.
Answer: B) Had disappeared.
Answer: D) By the time the vaccine was found, everybody had been a zombie.
Answer: A) Had moved.
Answer: A) He had written 10 books before he died.
Answer: D) Had seen.
Answer: D) Had run.
Answer: D) Subject + had + verb in past participle form.
Answer: A) I had heard.
Answer: D) Had opened.
Answer: B) Had you visited.
Answer: D) He had eaten dinner before she arrived.
Answer: A) Had expressed.
Answer: B) Had forgotten.
Answer: B) Had taken.
Answer: D) Had sunk.
Answer: A) Been extended.
Answer: A) Had left.
Answer: A) Had missed.
Answer: D) Hadn't/had not gone.
Answer: A) Had already left.
Answer: C) Had guessed.
Answer: A) True
Answer: C) Perfect
Answer: A) Clock had.
Answer: B) Had