Sure! Here are the filled-in blanks for the sentences in Exercise 4:

1. **Did** you start a community garden project last month?
2. Last week, we (not) **didn't** visit sick children in Viet Duc Hospital.
3. **Was** there anything that made you happy with your work last month?
4. It **was** Tom's fault. It's mine.
5. What **did** you do in the summer?
6. **Did** she visit Hue when she was a child?
7. Mimi and Lucy **were** at home in Florida last week. We were at Ben's house in Miami.
8. He (not) **didn't** come to the party last Sunday.
9. Julia (not) **didn't** wear uniform to school yesterday.
10. **Is** John at work today? - "No, he **isn't** in the office. I think he's sick."

For Exercise 5:

1. Children did not plant more trees.
(?) Did children plant more trees?

2. Tom was not a member of the Youth Club.
(?) Was Tom a member of the Youth Club?