Stop talking or you won’t understand the lesson.
A.If you stop talking, you won’t understand the lesson.
B.If you don’t stop talking, you won’t understand the lesson.
C.If you didn’t stop talking, you wouldn’t understand the lesson.
D.If you hadn’t stopped talking, you wouldn’t understand the lesson.

If I were a bird, I would fly high in the sky.
A.
B.Were I to be a bird, I would fly high in the sky.
C.Should I be a bird, I would fly high in the sky.
D.Had I been a bird, I would fly high in the sky.

The match can be cancelled because it rains heavily.
A.If it hadn’t rained heavily, the match couldn’t have been cancelled.
B.If it didn’t rain heavily, the match couldn’t be cancelled.
C.If it hadn’t rained heavily, the match couldn’t be cancelled.
D.If it doesn’t rain heavily, the match can’t be cancelled.

I didn’t go on holiday with my family because I was so busy.
A.If I wasn’t so busy, I would go on holiday with my family.
B.If I hadn’t been so busy, I would go on holiday with my family.
C.
D.If I hadn’t been so busy, I would have gone holiday with my family.

You would hear my explanation if you didn’t talk so much.
A.Unless you talked so much, you would hear my explanation.
B.Were you talked so much, you wouldn’t hear my explanation.
C.Were you talk so much, you wouldn’t hear my explanation.
D.Because you talked so much, you didn’t hear my explanation.

You didn’t read the instructions carefully, so you answered the wrong question.
A.If you read the instructions carefully, you would answer the wrong question.
B.If you had read the instructions carefully, you wouldn’t answer the wrong question.
C.Had you read the instructions carefully, you wouldn’t answer the wrong question.
D.If you had read the instructions carefully, you wouldn’t have answered the wrong question.

I’ll give you a call if I need some help tomorrow.
A.Should I need some help tomorrow, I’ll give you a call.
B.Had I need some help tomorrow, I would give you a call.
C.Were I to need some help tomorrow, I’ll give you a call.
D.Had I needed some help tomorrow, I would have given a call.

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.