A

There are 4 rooms in my house.

We mustn't throw garbage around the classroom

The Red River isn't as long as the Mekong River/The Red River is shorter than the Mekong River.

Vy is the best (student)in my class.

B

Lan's bedroom is small , but it's beautiful.

There is a bed near the desk.

There is a bookshelf next to the window.

There are many books on the bookshelf .

A. 
1. There are four rooms in my house.
2. We mustn't throw garbage around the classroom.
3. The Red River shorter than the Mekong River.
4. Vy is better than everyone in my class. 
B
1. Lan's bedroom is small, but it is beautiful.
2. There is a bed near to the desk.
3. There is a bookshelf next to the window.
4. There are many books on the bookshelf.