4. Children should take part in outdoor activities with their friends.

⇒⇒ What should children do?

5. Hoa's uncle bought her a bike.

⇒⇒ What did Hoa's uncle buy for her?

6. There are thousands of books in the public library.

⇒⇒ How many books are there in the public library?

7. I am going to visit my grandmother this Sunday.

⇒⇒ What are you going to do this Sunday?

8. They rarely eat out because it is far too expensive.

⇒⇒ Why do they rarely eat out?