Study hard or you won’t pass the exam.
A.
B.If you didn’t study hard, you wouldn’t pass the exam.
C.If you don’t study hard, you won’t pass the exam.
D.If you study hard, you won’t pass the exam.

I didn’t know you were coming, so I didn’t wait for you.
A.If I had known you were coming, I would have waited for you.
B.If I had known you were coming. I would wait for you.
C.Had I know you were coming, I would have waited for you.
D.I would have waited for you if I knew you were coming.

Without her teacher’s advice, she would never have written such a good essay.
A.
B.She wrote a good essay as her teacher gave her some advice.
C.If her teacher didn’t advise her, she wouldn’t write such a good essay.
D.Her teacher didn’t advise her and she didn’t write a good essay.

The car breaks down so often because you don’t take good care of it.
A.Were I to you, I would take good care of the car.
B.
C.If I took good care of the car, it wouldn’t break down so often.
D.Should you take good care of the car, it won’t break down so often.

If you arrive at the office earlier than I do, please turn on the air-conditioner.
A.Were you to arrive at the office earlier than I do, you can turn on the air-conditioner.
B.Should you arrived at the office earlier than I do, you can turn on the air-conditioner.
C.
D.Had you arrive at the office earlier than I do, you could have turned on the air-conditioner.

Call your parents; otherwise, they will worry.
A.If you call your parents, they will worry.
B.If you didn’t call your parents, they would worry.
C.Were you to call your parents, they would worry.
D.Unless you call your parents, they will worry.

The police stopped him because he drove so fast.
A.If he had driven so fast, the police wouldn’t have stopped him.
B.If he hadn’t driven so fast, the police wouldn’t have stopped him.
C.Had he drive so fast, the police wouldn’t have stopped him.
D.If he didn’t drive so fast, the police wouldn’t stop him.

He was in a hurry. He wanted to catch the bus.
A.
B.He was in a hurry in order to he would catch the bus.
C.He was in a hurry seeing that catch the bus.
D.He was in a hurry despite catching the bus.

They weren’t happy because they were disappointed with the result.
A.They weren’t happy due to they were disappointed with the result.
B.They weren’t happy despite the fact that they were disappointed with the result.
C.They weren’t happy because of being disappointed with the result.
D.They weren’t happy although they were disappointed with the result.

Choose the sentence which has the closest meaning to the original one.I don’t know the answer, so I can’t tell you.
A.If I know the answer, I will tell you.
B.If I had known the answer, I would have told you.
C.If I knew the answer, I will tell you.
D.If I knew the answer, I would tell you.