A sentence is given in the active voice. Choose the option that best expresses the same idea in the passive voice: "I would have kept your bicycle here if you had left it with me."

Introduction / Context:
Voice transformation questions test your understanding of how to convert sentences between active and passive while preserving tense, meaning, and conditional structure. The active sentence given is: I would have kept your bicycle here if you had left it with me. You must select the passive voice version that keeps the same conditional meaning and correct verb tense, focusing on your bicycle as the subject rather than I.

Given Data / Assumptions:

• Active sentence: I would have kept your bicycle here if you had left it with me.
• Subject in active: I.
• Object in active: your bicycle.
• Conditional clause: if you had left it with me (third conditional pattern).
• We need a passive structure with your bicycle as the subject.

Concept / Approach:
In the third conditional pattern, would have + past participle is used in the main clause, and had + past participle appears in the if clause to describe unreal past conditions. To change the main clause to passive voice, we move the object your bicycle to subject position and replace would have kept with would have been kept. The if clause, if you had left it with me, already contains the correct past perfect and need not be changed. The passive sentence should therefore read: Your bicycle would have been kept here if you had left it with me.

Step-by-Step Solution:
Step 1: Identify the object your bicycle in the active sentence and make it the subject of the passive sentence. Step 2: Recognise the main verb phrase would have kept and convert it to passive: would have been kept. Step 3: Keep the adverb here in the same position relating to the place where the bicycle would have been kept. Step 4: Leave the conditional clause if you had left it with me unchanged, as it already follows the third conditional pattern. Step 5: Put everything together: Your bicycle would have been kept here if you had left it with me, and compare with the options.

Verification / Alternative check:
Check that the meaning remains the same. The original sentence says that in a hypothetical past situation, the speaker would have kept the bicycle in this place if the listener had left it. The passive Your bicycle would have been kept here if you had left it with me expresses the same idea, simply focusing on the bicycle rather than the speaker. The tense would have been kept is consistent with would have kept, and the conditional if you had left it with me is preserved. This confirms that Option A is the correct transformation.

Why Other Options Are Wrong:
Keeping of your bicycle would have been done by me if you had left it.: This is grammatically awkward and unnatural, using a noun phrase keeping of your bicycle instead of a smooth passive verb form.
If you had left it with me I would have kept your bicycle there.: This remains in the active voice (I would have kept) and changes here to there, altering the original place reference.
Your bicycle would be kept there if you have left it with me.: This is wrong because it switches to a mixed conditional with would be kept and have left, which does not match the original third conditional structure.

Common Pitfalls:
Students often alter the tense when changing voice, especially in conditional sentences. Another common mistake is to form clumsy passive constructions using keeping of or done by instead of a simple be + past participle structure. To avoid these errors, always identify the type of conditional and the exact tense in the original sentence first, then systematically transform the main verb into passive while keeping the if clause tense unchanged.

Final Answer:
The correct passive form is Your bicycle would have been kept here if you had left it with me.