离心式压缩机在()范围内广泛采用。
A.小流量,低压力
B.小流量,高压力
C.大流量,高压力
D.大流量,低压力
参考答案:D
把下列各句改为被动语态。
1. We clean our classroom every day.
Our classroom _____ by us every day.
2. They produce silk in Suzhou.
Silk _____ in Suzhou.
3. They speak English in class.
English _____ in class.
4. He teaches us ten words every class.
Ten words _____ to us _____ every class.
5. We use keys for opening the door.
Keys _____ opening the door.
下列关于囊性肿物的描述,错误的是().
A.无回声性肿物
B.壁薄而光滑
C.后壁回声清晰而锐利
D.具有后方声影
E.内部无多普勒血流信号