Identify the correct Passive Voice form of the following sentence.
Who did this?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → By whom was this done?
Passive of a "Who" question:
| Change | Active | Passive | Why |
|---|---|---|---|
| Agent (by ...) | Who | By whom | “Who” (the doer) becomes “By whom” at the start of the question. |
| Tense kept | did | was ... done | Simple past “did” becomes was / were + past participle: “was done”. |
| Object becomes subject | this (object) | this (subject) | The object “this” becomes the subject, placed after the helping verb because the sentence is still a question. |
| Full sentence | Who did this? | By whom was this done? |
Example: Who wrote this letter? → By whom was this letter written?
Why the Other Options are Incorrect?
Option 1: Who has done this? — Incorrect. It is still in the active voice, and the tense has changed to present perfect.
Option 2: This is done by whom? — Incorrect. "Is done" is present, not past, and the question keeps the word order of a statement.
Option 4: Lets me know who has done this? — Incorrect. It turns the question into a faulty request ("Lets" for "Let"), stays active and changes the tense.