This proposal is objected to by us.
Which one of the following is the correct active structure corresponding to the above sentence ?

The correct answer is Option C (We object to this proposal.).

Key Points:
• This question evaluates the candidate's understanding of converting Passive Voice to Active Voice, focusing on verbs with fixed prepositions, a common MPSC testing area.
• Option 3 is the correct answer according to the official MPSC answer key. In the passive sentence, the verb 'objected' is followed by the fixed preposition 'to'. When converting to active voice, the object of 'by' ('us') becomes the subject ('We'), the present tense verb is retained ('object'), the fixed preposition is preserved ('to'), and the original subject becomes the object ('this proposal').
• Let us analyze why the other options are flawed. Option 1 incorrectly drops the essential preposition 'to' and pairs the plural 'these' with the singular 'proposal'. Option 2 remains in the passive voice and merely drops the agent. Option 4 changes the entire grammatical structure and word class, using 'subject to objection' rather than the active verb.
• A common MPSC trap is dropping the preposition (like 'to', 'at', 'with') associated with the verb during voice transformation.
• Always retain fixed prepositions attached to verbs when switching between active and passive voices.
• Key Takeaway: Remember: When a verb takes a fixed preposition (e.g., object to, laugh at), the preposition must be retained in both active and passive voices.