The correct word or phrase that

the correct word or phrase that best fits each of the HUD
In recent years there have been many articles on air pollution in newspapers and
magazines. Scientists all over the world have warned that our atmosphere is becoming more
and more (1)_ and that man, through his carelessness, may run out of fresh air to
breathe.
are
Automobiles and industries mainly (2) for air pollution in most cities. They pour
into the air such gases as carbon monoxide, sulphur and nitrogen oxides, (3)
very harmful to humans. Worse still, these gases after a series of chemical changes, turn
into toxic acids. They fall down in "acid rains" raising the acidity in the air, soil, water
affecting not only trees but also fish and other wildlife. Many industrial countries
Europe and North America have suffered bad effects from those "rains".
Scientists, social organisations and governments should sit down together to
the air pollution problem.
(4)
(5)
(6)
Question 1. A. pollute
Question 2. A. account
B. pollution
B. behave
C. pollutant
D. polluted
C. bring
D. install
C. who
D. which
C. yet
D. so
C. on
D. for
B. solve
C. spray
D. drip
Question 3. A. whose
Question 4. A. but
Question 5. A. to
Question 6. A. conserve
B. whom
B. and
B. in
lotter A. R. C or D on your answer sheet to indicate the correct answer to each of