The air / many areas / so unclean that / people / have to / masks / going / streets
A.
B.
C.
D.

Industrial factories / throw / air / huge amounts / pollutant gases
A.
B.
C.
D.

Smoke / aircrafts / factory chimneys / bonfires / different kinds of vehicles / streets / many / other factors / damage / clean air / every day
A.
B.
C.
D.

One / biggest environmental impacts of human activities / air pollution
A.
B.
C.
D.

The trees in this area were                    off for crops and the construction of public facilities.
A.
B.
C.
D.

The trees in this area were                    off for crops and the construction of public facilities.
A.
B.
C.
D.

To                means to set up or initiate.
A.
B.
C.
D.

                   is a process by which green plants and other organisms turn carbon dioxide and water into carbohydrates and oxygen, using light energy.
A.
B.
C.
D.

Consumers have been                   to use environmentally friendly products.
A.
B.
C.
D.

Air pollution / lead / greenhouse effect / make / temperature / Earth's surface / higher
A.
B.
C.
D.