Question

Who was knocking at the door?change into passive voice

Answer 1

By whom was the door being knocked?

Answer 2

Answer:

Passive voice: The door is knocked by whom?

EXPLANATION:  

The subject performs the action which is denoted by the verb in an active voice sentence. There is a general rule to be followed while changing active voice into passive voice.

1. Identify the sentence pattern and segregate the sentence in SVO pattern.
2. Now reframe the sentence in OVS pattern (First object is placed which is followed by verb and subject).
3. The tense should not be mismatched.

Now, after applying all these rules, the passive voice of the given sentence is written as “The door is knocked by whom?”