截止阀是无方向性的阀门。
参考答案:错
-Do you have any plans for Saturday?
-To tell you the truth, I have nothing in ________ for Saturday.[ ]
A.head
B.mind
C.heart
D.brain
流产的类型()
A.先兆流产
B.习惯性流产
C.难免流产
D.不全流产
E.完全流产