Câu điều kiện loại 2: 1/ I don't know what to say to her. ` -> ` What 2/ They are too old to take part in the social activities. ` -> ` If they 3/ I find it difficult for me to read the letter because it is very dark. `-> `Unless

`1.` What to say to her is which I don't know.

`-` What clause + V + is/was + câu/từ được dùng để nhấn mạnh.

`2.` If they weren't too old , they could take part in the social activities.

`-` Câu điều kiện loại `2 :` If S + Ved/V2 , S + would/could/might + V-inf

`3.` Unless it is very dark , I won't find it difficult for me to read the letter.

`-` Câu điều kiện loại `1 :` If S + V hiện tại , S + will/can/may + V-inf

`-` Unless `=` if not : nếu không