单项选择题

Questions 9 and 10 are based on the following news. At the end of the news item, you will be given 20 seconds to answer the questions. Now listen to the news. According to the news item, the atmosphere that blocks harmful ultraviolet rays

A. shrinks and expands regularly recently.
B. is closely connected to sun’s activity.
C. absorbs carbon dioxide at high altitude.
D. is largely influenced by the movement of satellites.