Here are the completed sentences:

1. It might rain. We’d better **take** an umbrella.
2. Ben needs to know what happened. Somebody **should** better tell him.
3. We’d better **not** park the car here. The road is too narrow.
4. You **should** brush your teeth at least twice a day.
5. What are we going to do? It’s time **to** decide.
6. It’s time they **did** better not be late. It’s an important meeting.
7. It’s time they **were** here. They promised they wouldn’t be late.
8. The window is open. You’d **better** close it before you go out.
9. We’d better leave as soon as possible, **hadn’t** we?
10. The government should **do** something about the problem.
11. It’s time the government **had** something done about the problem.
12. It’s time something **was** done about the problem.