The workers had built the wall. (Passive)

  1. The wall had built by the workers.
  2. The wall had been built by the workers.
  3. The wall was built by the workers.
  4. The wall has been built by the workers.
Answer

B) The wall had been built by the workers.

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

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