6. D.

7. A.

8. A.

9. A.

1. This flower is being watered by my father every morning.

2. Fiona was invited to the birthday party last night by John.

3. The dinner is being prepared by her mother in the kitchen.

4. Our teeth should be cleaned twice a day.

Isn't writing

You shouldn't stay up so late to listen to music.

S + should(n't) + V-inf + O.

C. Where is chosen

The city là địa điểm nên dùng where

Nếu dùng D. thì sẽ bị thiếu tobe 

Nên ta chọn C.