`1`. I saw a lot of people and horses that went to the market.

`-` Đại từ quan hệ: that: thay thế cho who/ which/ whom, nếu trong câu không có dấu phẩy.

`2`. Tom has three sisters, who are married.

`-` Đại từ quan hệ: who

`+` Chỉ người

`+` Thay thế cho I, we, you, they, she, he, N ( chỉ người)

`+` Sau nó là V

`3`. I recently went back to Paris, which is still as beautiful as a pearl.

`-` Đại từ quan hệ: which

`+`  Chỉ sự vật/ sự việc

`+` Thay thế cho S/ O

`+` Theo sau là V/ S

`4`. I recently went back to Paris, where I was born nearly `50` years ago.

`-` Đại từ quan hệ: where `->` dùng để chỉ nơi chốn

`5`. 

1. I saw a lot of people and horses that went to market

That thay thế cho cả người lẫn vật trước nó

2. Tom has three sisters who are married

Who thay thế cho người đứng trước nó

3. I recently went back to Paris which is still as beautiful as a pearl

Which thay cho vật đứng trước nó

4. I recently went back to Paris in which I was born nearly 50 years ago

in which = where thay thế cho một địa điểm trước nó