De 4

Cau 1

/s/: lakes; roofs; steps; tops

Cau 2

1, is cleaned

2, has been

3, was doing

4, were

5, eats

6, to do

Cau 3

1, isn’t -> doesn’t

2, because -> so

3, who -> whom

4, living -> live

5, or -> and

6, more -> the most

Cau 4

1, learning

2, are

3, of

4, you

Cau 5

1, They are very important to the world’s climate.

2, Amazon rain forests produce about 30 to 40 percent of oxygen on the earth.

3, The decreasing size of rain forests will affect the climate on the earth.

4, No, it isn’t.

Cau 6:

1, … going to the swimming pool.

2, … to turn down the radio for him.

3, … studied English for four years.

4, … city has been destroyed by an earthquake.

Cau 7

1, John became a professional footballer at the age of 15.

2, We used to wear uniforms when we were at school.