他们肯定已经走了——外套不见了，门也锁了。
They must have left already since their coats are gone and the door is locked.
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must英 /mʌst/|美 /mʌst/
left英 /lɛft/|美 /lɛft/
解释
must have 是对过去动作的推测，left 是 leave 的过去分词，表示根据「外套不见+门锁」推断「已经离开了」
They must have left already since their coats are gone and the door is locked.
must have 是对过去动作的推测，left 是 leave 的过去分词，表示根据「外套不见+门锁」推断「已经离开了」