Question Detail

Post this letter.

Let this letter be post.
Let this letter be posted.
Let this post be letter.
Let this letter is posted.
Let this letter are posted.

Answer: Option B

1. He had written a poem.

A poem has written by him.
A poem had written by him.
A poem had been written by him.
A poem has been written by him.

Answer: Option C

Explanation:

Note :- Rule to make active voice of Past Perfect Tense :

Passive subject + had + been + third form of verb + by + passive object

2. There is nothing to do.

There was nothing to be done.
There is nothing to be done.
There is nothing to done.
There is no thing to do.

Answer: Option B

3. Someone has stolen his book.

His book is been stolen.
His book has been stolen.
His book is stolen.
His book has stolen.

Answer: Option B

Explanation:

Apart from Rule to make active voice of Present Perfect Tense, which is

Passive subject + has/have + been + third form of verb + by + passive object

Please also note that words like, "someone", "somebody", "people", "police", "public" etc are dropped. But in rare cases we can use them if sentence meaning is not clear.