`1.` Thang enjoyed chatting with his friend by face-to-face.

`2.` In Sweden, people call each other by their first name.

`3.` We don't like playing computer games.

`4.` She used to look after her younger brothers and sisters.

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`1.` I study English so as to read books in English.

Giải thích: so as to V: để mà

`2.` Because of the dangerous acid rain, trees' leave are damaged.

Giải thích: Because + Mệnh đề = Because of + N/V-ing.

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`1.` has become (trước since ta chia HTHT: have/has been)

`2.` will be waiting (thì tương lai tiếp diễn hành động đang diễn ra tại một thời điểm xác định trong tương lai: will be V-ing)

`3.` chatting (chatting online: nhắn tin trên mạng)

`4.` to phone (try to V: cố gắng làm gì)

@ `Ly`

1.Thang enjoyed chatting with his friends by face to face

4. She used to look after her younger brother and sister

2. In Sweden, people call each other by their first name

3. We don't like playing computer games.

Ques 2. Has become, will be waiting, chatting, to phone hoặc phoning 

read books in English

the fact that acid rain is dangerous , trees' leaves are damaged.