Ответ:

1.

1. If you are busy, I shall leave you alone.

2. If you were busy, I should leave you alone.

3. If you had been busy, I should have left you alone.

2.

1. If my friend comes to see me, I shall be very glad.

2. If my friend came to see me, I should be very glad.

3. If my friend had come to see me, I should have been very glad.

3.

1. If mother buys a cake, we shall have a very nice tea party.

2. If mother bought a cake, we should have a very nice tea party.

3. If mother had bought a cake, we should have had a very nice tea party.

4.

1. If we receive a telegram from him, we shall not worry.

2. If we received a telegram from him, we should not worry.

3. If we had received a telegram from him, we should not have worried.

5.

1. If you don’t work systematically, you will fail the exam.

2. If you did not work systematically, you would fail the exam.

3. If you had not worked systematically, you would have failed the exam.

6.

1. If I live in Moscow, I shall visit the Tretyakov Art Gallery every year.

2. If I lived in Moscow, I should visit the Tretyakov Art Gallery every year.

3. If I had lived in Moscow, I should have visited the Tretyakov Art Gallery every year.

7.

1. If I get a ticket, I shall go to the Philharmonic.

2. If I got a ticket, I should go to the Philharmonic.

3. If I had got a ticket, I should have gone to the Philharmonic.

8.

1. If I live near a wood, I shall gather a lot of mush-rooms.

2. If I lived near a wood, I should gather a lot of mushrooms.

3. If I had lived near a wood, I should have gathered a lot of mushrooms.

9.

1. If my father returns early, we shall watch TV together.

2. If my father returned early, we should watch TV together.

3. If my father had returned early, we should have watched TV together.

10.

1. If she knows English, she will try to enter the university.

2. If she knew English, she would try to enter the university.

3. If she had known English, she would have tried to enter the university.