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