`1.` We can't swim in the river because it's very dirty.

`->` clause + because + clause: bởi vì...

`2.` If you don't work hard, you will not pass your exam.

`->` Điều kiện loại `1:`

`(-)` If + S + do/does not + V-bare, S + will/can/shall + V-bare

`3.` Although my brother plays tennis very well, he didn't win the game yesterday.

`->` Although + clause, clause: mặc dù...nhưng...

`4.` I won't be able to attend the meeting next week since I'll be on vacation.

`->` clause + since + clause: bởi vì...

`5.` Unless you start working hard now, you won't be able to pass the final test.

`->` Điều kiện loại `1:`

Unless/If + S + V-(s/es), S + will/can/shall + V-bare

`-` Unless `=` If not

`1` We can't swim in the river because it's very dirty.

`-` because + mệnh đề nguyên nhân: bởi vì 

`2` If you don't work hard, you won't pass your exam.

`-` Điều kiện loại 1: Diễn tả sự việc có thật ở hiện tại (tương lai)

`->` If + S + V (s,es), S + will/can/may + V0 

`3` Although my brother plays tennis very well, he didn't win the game yesterday.

`-` Mệnh đề nhượng bộ: 

`@` Although/ Even though/ Though + S + V: mặc dù 

`-` S + be + good at + Ving = S + V + well 

`4` I won't be able to attend the meeting next week since I'll be on vacation.

`-` since + mệnh đề nguyên nhân: bởi vì 

`5` Unless you start working hard now, you won't be able to pass the final test.

`-` Điều kiện loại 1: (như trên)

`-` Unless + mệnh đề khẳng định = if ... not : nếu không