`1` Tet, which occurs in late January or early February, is a festival. 

`-` ĐTQH which dùng để thay thế N (vật)

`2` I like reading books which tell about different peoples and their cultures.

`-` ĐTQH which dùng để thay thế N (vật)

`3` The class watched a film which was about the Apollo 13 space mission.

`-` ĐTQH which dùng để thay thế N (vật)

`4` We read about an astronaunt who travelled into space in 1961.

`-` ĐTQH who dùng để thay thế N (người) đóng vai trò chủ ngữ

`5` This is a man who works for NASA.

`-` ĐTQH who dùng để thay thế N (người) đóng vai trò chủ ngữ

Giải thích:

`-` who thay thế cho N chỉ người ở chủ ngữ

`->` N (chỉ người) `+` who `+` V(chia) `+` O..

`-` which để thay thế N chỉ vật.

`->` N (chỉ vật) + which + V + O..

`->` N (chỉ vật) + which + S + V..

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`1,` Tet is a festival which occurs in late January or early February. 

`2,` I like reading books which tell about different people and their cultures.

`3,` The film which the class watched was about the Apollo `13` space mission. 

`4,` We read about an astronaut who travelled into space in `1961`.

`5,` This is the man who works for `NASA`.