Ответ:

1ex

1. is

2. are

3. is

4. are

5. is

6. are

7. is

8. am

2ex

1. It isn't hot today.

2. I'm not at home.

3. My friends aren't here.

4. You aren't a teacher.

5. We aren't at the cinema.

6. This isn't difficult.

7. Sam isn't happy.

3ex

1. Am I late?

2. Are you ill?

3. Are we right?

4. Is he fifteen?

5. Is it cold?

6. Is this school in this street?

7. Are my books in your bag?

4ex

1-c)

2-a)

3-e)

4-b)

5-d)