Complete each of the following sentences by choosing the option that most suitably fills the space;
Before the operation, the dentist found that his patient's teeth....
A. have long decayed B. have long been decayed C. have long being decayed D. had long decayed E. had been decayed
Correct Answer: D
Explanation
When you need to talk about two things that happened in the past and one event started and finished before the other one started, place “had†before the main verb for the event that happened first.
