单项选择题
Questions 17 to 20 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.
Why do the cheerleaders sometimes suffer physical injuries（）
A．Because they try dangerous acts to catch people’s attention.
B．Because they shout and yell so their voice becomes hoarse.
C．Because they go to the pyramid and the hills to perform.
D．Because they dance too much every day for practice.