Answer: C) Had changed.
Explanation for this question is being written.
Answer: B) Had just gone.
Answer: B) Had changed.
Answer: B) When I left the office, I had been working on the report all day.
Answer: B) Had practiced.
Answer: D) Had already left, got.
Answer: A) Had to arrange.
Answer: C) Had left.
Answer: B) Had
Answer: C) Past perfect Tense.
Answer: B) Doctor Harvey had built the first artificial brain.
Answer: C) Had arrived.
Answer: B) Had been finished.
Answer: B) Had watched.
Answer: C) Had gone.
Answer: D) Had
Answer: B) Hadn't ever used.
Answer: B) Had + past participle.
Answer: C) I had left.
Answer: B) Had been locked.
Answer: B) Past perfect.
Answer: B) Had studied.
Answer: D) Had / never / visited.
Answer: B) Past Perfect.
Answer: D) Had written / was.
Answer: A) Had
Answer: C) Past Perfect.
Answer: C) Had eaten.
Answer: A) Had left.
Answer: D) Past Perfect.
Answer: A) Had listened.
Answer: B) Had never used.
Answer: B) Had already.
Answer: B) Had started.
Answer: A) Past perfect.
Answer: B) Had been submitted.
Answer: A) Had changed.
Answer: B) Had checked.
Answer: D) Had already started.
Answer: C) Had donated.
Answer: C) Had been.
Answer: C) Had rained.
Answer: C) Had finished.
Answer: A) Had known.
Answer: C) You helped.
Answer: D) Hadn't lent.
Answer: D) Had tried.
Answer: D) Had played.
Answer: A) Listened
Answer: A) Had I switched off.
Answer: B) Had they read.
Answer: A) Had been completed.
Answer: D) Had been reviewed.
Answer: A) Had planted.
Answer: D) Couldn't-had applied.