knock at the door和knock on the door到底有什么区别
knock at the door ，敲门; 叫门; [例句]There had been a knock at the door and when she opened it she locked herself out.外面有敲门声，她去开门，结果把自己反锁在了外面。knock on the door 敲门声; 敲门; [例句]To his relief a loud knock on...
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knock at the door ，敲门; 叫门; [例句]There had been a knock at the door and when she opened it she locked herself out.外面有敲门声，她去开门，结果把自己反锁在了外面。knock on the door 敲门声; 敲门; [例句]To his relief a loud knock on...
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