The patient won’t recover unless he undergoes an operation.
A.The patient wouldn’t recover if he didn’t undergo an operation.
B.The patient won’t recover if he didn’t undergo an operation.
C.The patient won’t recover if he doesn’t undergo an operation
D.The patient wouldn’t have recovered if he hadn’t undergone an operation.

She doesn’t take any exercises. She is so unhealthy.
A.If she takes some exercises, she will be healthy.
B.
C.If she had taken some exercises, she would have been healthy.
D.If she had taken some exercises, she would be healthy.

If the weather is fine, we will go camping.
A.Should the weather is fine, we will go camping.
B.Should the weather be fine, we will go camping.
C.Were the weather to be fine, we will go camping.
D.

If you don’t speak loudly, our teacher won’t hear.
A.Unless you don’t speak loudly, our teacher won’t hear.
B.
C.If you speak loudly, our teacher won’t hear.
D.Unless you speak loudly, our teacher won’t hear.

Without water, we would die.
A.If there is no water, we will die.
B.If there is no water, we would die.
C.If there was no water, we would die.
D.If there were no water, we would die.

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.