听第二篇短文，回答第 16 至 20 小题。
(
)16. How many kinds of pollution are mentioned?
A. Three.
B. Four.
C. Five.
(
)17. What will create air pollution?
A. Using chemicals.
B. Putting rubbish into the land.
C. Burning gas, oil and coal.
(
)18. What can air pollution cause?
A. Breathing problems.
B. Much litter.
C. Hearing loss.
(
)19. What may cause high blood pressure?
A. Air pollution.
B. Noise pollution.
C. Light pollution.
(
)20. What does the speaker want to tell us?
A. What pollution is.
B. Why there are many kinds of pollution.
C. We should protect our environment.
