There are many medical problems in the modern society. One of the most alarming medical problems in the world is a【21】disease named HIV virus. This kind of virus is first【22】twenty years ago. It weakens the body and develops fully blown AIDS. AIDS is not obvious in the early stage. Sometimes symptoms occur within a few weeks after【23】. They are often flu-like, such as【24】, fever, headache, diarrhea and night sweats.
The three main【25】routes of HIV are sexual contact, exposure to infected body fluids or tissues and from mother to【26】or child during perinatal period. This kind of virus can always【27】some families apart. People's first【28】is a denial about their loved one's condition. HIV positive people are those who have tested positive for the virus.【29】they are related to conditions that are far less serious than HIV, they can only be treated when potential patients are【30】of the risk of infection. They choose to deal with the risk instead of avoiding of it.
【31】tests are the best way to monitor HIV because they can slow the progress of the virus【32】time. But we have to admit that it is no longer associated【33】death immediately, but drugs are not【34】. Doctors【35】HIV positive people to have regular tests to monitor the progress of the disease.
By now there is still not successful vaccination against HIV, so much effort has been【36】mainly on educating the public about【37】HIV is passed on. In addition, more emphasis is contributed to introduce to the citizens about personal measures that【38】the risk of infection. "We are concerned about these individuals, because we know that early treatment can help【39】their life and ensure that they do not【40】others, including their newborn children. " Dr Donald Gelhorn (president of the College of Family Physicians of Canada) says.
(21)

A. serious
B. deadly
C. tough
D. dangerous