单项选择题

Questions 14 to 17 are based on the following passage. At the end of the passage, you will be given 20 seconds to answer the questions.
Now, listen to the passage.

Which element determines the harm brought by the noise pollution

A.Frequency and intensity of the sound.
B.The time the pollution lasts.
C.The density of the population.
D.The quality of the sound.