They had completed the project. (Passive)

  1. The project was completed by them.
  2. The project has been completed by them.
  3. The project had been completed by them.
  4. The project had completed by them.
Answer

C) The project had been completed by them.

Past perfect → had been + V3. Active & Passive Voice · Voice in tenses

English MCQ · More English: Active & Passive Voice MCQs · Practise