Concept:The passive voice uses a form of "be" + past participle. To change it to active voice, we must find or add a subject (doer) and make the original subject the object.
Explanation:The given sentence uses the past perfect passive: "had not been expected." No agent (doer) is mentioned, so we add a vague subject like "someone" or "they."
• Convert the verb to active past perfect: "had not expected."
• The original subject "the offer" becomes the object.
• The rest "to be withdrawn at the last moment" stays the same because it is an infinitive phrase.
Option A correctly follows this: "Someone had not expected the offer to be withdrawn at the last moment."
Option B changes the structure and tense (simple past "was not expected") and is still passive.
Option C invents a wrong meaning (offer withdrawing itself) and drops the expectation.
Option D changes tense to simple past and uses active "withdrew," which alters the original passive sense.
Answer:Option A: Someone had not expected the offer to be withdrawn at the last moment.