`1` Before my mother came home , my father had watered all the plants in the garden

`=>` Before = by the time 

`2` If I knew her number , I would ring her up.

`=>` Mệnh đề if loại 2 : If + quá khứ đơn , + would/could + V 

`3` If knew the answer, I could tell you

`=>` Mệnh đề if loại 2 : If + quá khứ đơn , + would/could + V 

`4` If the people protected the environment now , the evironment would be nicer

`=>` Mệnh đề if loại 2 : If + quá khứ đơn , + would/could + V 

`5` If they had a map , they would got lost 

`=>` Mệnh đề if loại 2 : If + quá khứ đơn , + would/could + V 

`6` Many houses were destroyed by the storm in this village last week

`=>` Câu bị động thì quá khứ đơn : S + was/were + V3/ed + By O 

1. I don’t know her number, so I don’t ring her up

 If I knew her number, I would ring her up.

2. I don’t know the answer, so I can’t tell you.

 If I knew the answer, I could t tell you.

3. When you ask me for the book, I will lend it to you.

Unless you ask me for the book, I won't lend it to you.

4. I feel miserable because Kate doesn’t love me.

 If Kate loved me, I wouldn't feel miserable.

5. I won’t go to the party because I’m not feeling well.

 I would go to the party if I felt well.

6. There are too many cars. As a result, our planet is polluted.

 If there weren't too many cars, our planet wouldn't be polluted.