卧式活塞机的支承环只是为活塞定心导向。
参考答案：错
声像图显示肾囊肿要具备的标准是（）。
A.无回声结构
B.包膜完整光滑
C.后方声加强
D.以上各项均是
He ____ in the factory since he left school ten years ago.[ ]
A. works
B. worked
C. was working
D. has worked
