1. Trees can keep water from___(run)away. 2. He did not know his...答:1, running, from是介词,后面加动词ing 2 d,he did not know , 是过去式,而他父母走是在这之前,所以应该是过去完成时 3,about , nervous about 固定短语,因为什么而担心 4 , C, 从什么变成什么,用TO 5,D, so that ,以便于 固定短语。符合句意 6, C虚拟语气,suppose, 是假设...