Which bank serves the public best ?
Select the correct passive voice of the sentence.
a. By which bank the public is served best ?
b. By which bank is the public served best ?
c. Which is the bank that served the public best ?
Answer options :

The correct answer is Option B (Only b).

Key Points:
• This question evaluates the candidate's understanding of Active and Passive Voice, particularly for interrogative sentences, a crucial grammatical concept frequently tested in MPSC exams.
• Option 2 is the correct answer according to the official MPSC answer key. When converting an interrogative sentence starting with 'Which + noun' into the passive voice, the structure changes to 'By which + noun + auxiliary verb + object + past participle'. Thus, 'By which bank is the public served best?' strictly follows interrogative inversion rules.
• Let us analyze why the other options are grammatically flawed. Option 'a' fails because it lacks the necessary interrogative inversion; 'the public is' forms an assertive clause order rather than a question order. Option 'c' completely alters the sentence structure into a complex sentence and incorrectly shifts the tense from present ('serves') to past ('served').
• A common MPSC trap is forgetting to invert the subject and auxiliary verb in passive interrogative sentences.
• Consistent practice of voice conversion rules ensures higher accuracy and prevents unnecessary loss of marks.
• Key Takeaway: Remember: In passive interrogative sentences, the auxiliary verb must precede the new subject (e.g., By whom is this done?).