Change the voice: You seem to have made a mistake.

The correct answer is "A mistake seems to have been made by you." The active sentence is: "You seem to have made a mistake." This contains a complex infinitive structure "seem to have made". To convert this to passive voice:

• The object "a mistake" becomes the subject.
• The infinitive "to have made" becomes "to have been made".
• The subject "you" becomes "by you".
• The verb "seem" remains in the present tense.

This gives us: "A mistake seems to have been made by you."

• "A mistake had been made" – incorrect tense (past perfect).
• "A mistake is being made" – changes the meaning to present continuous.
• "A mistake has made" – grammatically incorrect structure.

Hence, the correct passive voice is "A mistake seems to have been made by you."