单项选择题
Questions 20 and 21 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.
The strikers are denied entry into the US because（）
A．AIDS virus has been found among them.
B．they can not get political asylum in the US.
C．the US government has refused to take them.
D．they don’t accept proper medical treatment.