题目

Tell John not to leave the house________he makes sure that all the lights are turned off.  A．unless                                             B．if   C．once                                                 D．because 答案：A　考查连词。句意为：告诉约翰不要离开房间，除非他确保所有的灯都关上了。unless意为“除非，如果不”。

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