The structure “would rather” is followed by the past tense when expressing a present or future preference about someone else’s action.
👉 Structure:
I would rather + subject + past tense
So the correct sentence is:
“I would rather you didn’t smoke indoors.”
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Other options explained:
• A) won’t smoke – future tense (not used after “would rather”)
• B) doesn’t smoke – incorrect tense (present)
• C) don’t smoke – wrong verb agreement for “you” in this structure