虚拟语气中的shouldLet me know if you should hear more news.万一听到更多消息,请告诉我。in case ofIn case of rain they can't go.万一下雨,他们就不能去了。provided (that)Provided that circumstances permit, we shall hold the meeting next week.只要情况允许,我们下周将举行会议。on condition thatI will go abroad on condition that my husband goes with me.如果我丈夫能和我一起去, 我就出国。