Question

He had delivered the letters (change into passive voice)​

Answer 1

The answer is:

below

Step-by-step explanation:

Here's the right answer for your question.

The sentence "He had delivered the letters" is in active voice; let's change it to passive:

The letters had been delivered by him.

Hence, this is the answer.

Answer 2

He had the letters delivered.

Step-by-step explanation:

subject + auxiliary verb + object + verb in past participle