题目

_____ in the mountains for a week, the two students were finally saved by the local police.  A. Having lost       B. Being lost                C. Lost                 D. Losing 答案：C下面说法中正确的是A.正在振动的物体不一定发声B.一切正在发声的物体都在振动C.只要物体振动，人耳就一定能听到D.蝙蝠发出的超声波，不是由振动产生的