$\text{Đáp án :}$

`1` . The girl who lived next door to us is very friendly.

`->` Who thay cho "the girl" dùng để chỉ người

`2` . Because it rained heavily , they were late for school.

`->` Because + S + V : bởi vì `-` chỉ nguyên nhân

`3` . I enjoy reading book in my free time.

`->` enjoy doing sth = interested in doing sth : thích làm gì

`4` . Hellen should prepare her homework more carefully .

`->` Should do sth : nên làm gì

`Chan`

1. The girl who lived next door to us is very friendly

Who là mệnh đề quan hệ thay cho " the girl " để chỉ người

2. Because it rained heavily , we were late for to school

( Because + S + V-infinitive )

3. I enjoy reading book in my free time.

( S + enjoy(s) + V-ing + something )

4. Hellen should prepare her homework more carefully .

 Should + do sth