`1`. He can't go out because he has to study for his exam.
`→` If he didn’t have to study for his exam, he could go out.
`2`. She is lazy so she can't pass the exam.
`→` If she weren’t lazy, she could pass the exam.
`3`. He smokes too much, that's why he can't get rid of his cough.
`→` If he pays me tonight, I will have enough money to buy a car......
`4`. I can't play football this afternoon because I felt tired.
`→` If I hadn't felt tired, I could play football this afternoon.
`5`. Olga and Ivan weren't paying attention, so they didn't see the sign marking their exit from the highway.
`→` If Olga and Ivan had been paying attention, they would have seen the sign marking their exit from the highway
`6`. She can't be employed because she doesn't have a college degree.
`→` If she had a college degree, she could be employed
`7`. She walked to the meeting. She was late.
`→` If she hadn't walked to the meeting, she wouldn't have been late
`8`. Unless you promise to return back, I won't lend you.
`→` If you don't promise to return back, I won't lend you
`9`. We put off our trip because the weather was terrible.
`→` If the weather hadn't been terrible, we wouldn't have put off our trip
`10`. Sally doesn't know what she has to do for homework because she was absent from school on Friday.
`→` If Sally hadn't been absent from school on Friday, she would know what she has to do for homework
`→` Cấu trúc:
`0`. If + S + V(s,es), S+ V(s,es)/câu mệnh lệnh
`→` Điều kiện diễn tả thói quen, sự thật hiển nhiên
`1`. If + S + V(s,es), S + Will/Can/shall…… + V
`→` Điều kiện có thể xảy ra ở hiện tại ở tương lai
`2`. If + S + V2/ Ved, S +would/ Could/ Should…+ V
`→` Điều kiện không có thật ở hiện tại
`3`. If + S + Had + V(pp)/Ved, S + would/ could…+ have + V(pp)/Ved
`→` Điều kiện không có thật trong quá khứ
`4`. If + S + had + V3/Ved, S + would + V