Step 1: Understanding the Concept:
Interrogative sentences starting with ``Who'' require a specific transformation in the passive voice.
The subject pronoun ``Who'' changes into the object pronoun ``Whom'' and is usually placed at the beginning of the sentence preceded by the preposition ``By.''
Crucially, because it is still a question, the sentence must maintain Inverted Word Order (Verb before Subject).
Step 2: Detailed Explanation:
Let's convert the sentence step-by-step:
1. Identify the tense: ``did'' is the Simple Past tense.
2. Identify the Object: ``this damage'' is the object of the active sentence.
3. The Formula: By whom + was/were + Object + V3?
- We use ``was'' because ``this damage'' is an uncountable/singular noun.
- The V3 of ``do'' is ``done.''
4. Application: By whom (Who $\to$ By whom) + was (Auxiliary) + this damage (New Subject) + done (V3)?
Why other options are wrong:
- Option (B) ``Who was this damage done by?'' is acceptable in informal speech but is generally considered secondary to the ``By whom'' construction in strict academic tests.
- Option (C) ``By whom this damage was done?'' is a common trap. It fails because it uses Assertive word order (Subject ``damage'' before Verb ``was''). In a question, the verb must come first.
- Option (D) changes the tense to Past Continuous (was doing), which is incorrect.
Step 3: Final Answer:
Option (A) is the grammatically precise and formally correct passive transformation of the active question.