1. My salary must be increased or I will look for another job

--> if

--> unless

2. If I hadn't been so busy, I would have written to you earlier --> Beacause

`color{pink}{Vanie}`

`1`.

`->` If my salary is not increased, I will look for another job.

`+` If + S + be(not) + adj, S + will + V-inf: Nếu...., sẽ....

`->` Unless my salary is increased, I will look for another job.

`+`Unless + S + adj + ..., S + will + V-inf: Trừ khi...., thì...

`2`.

`->` Because I was so busy, I didn't write to you earlier.

`+` Because + S + be + O, S + V-inf + ...: Bởi vì

`1.`

`->` If my salary isn't be increased, I will look for another job.

`->` Unless my salary is increased, I will look for another job.

`-` S + must + V(bare) + or + S + will/can/may/... + V(bare)

`->` Câu điều kiện loại 1: If + HTĐ (S + V-s/es), S + will/can/may/... + V(bare)

`->` Unless + HTĐ (S + don't/doesn't + V-inf), S + will/can/may/... + V(bare)

`2.` Because I was so busy, I didn't write to you earlier.

`-` Câu điều kiện loại 3: If + QKHT (S + hadn't + been + N/Adj), S + would/could/might + have + V3/ed

`->` Because + Clause 1 (S + was/were + N/Adj), Clause 2 (S + didn't + V-inf): Bởi vì