1. AIDS is the final, life-threatening stage of infection with human immuno-deficiency virus(HIV). AIDS stands for acquired immu

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问题 1. AIDS is the final, life-threatening stage of infection with human immuno-deficiency virus(HIV). AIDS stands for acquired immuno-deficiency syndrome. The name refers to the fact that HIV severely damages the patient’s disease-fighting immune system. Cases of AIDS were first identified in 1981 in the United States, but researchers have traced cases to as early as 1969. Millions of AIDS cases have been diagnosed worldwide.
2. AIDS is caused by two viruses that belong to a group called retroviruses. The first AIDS virus was isolated by researchers in France in 1983 and researchers in the United States in 1984. This virus became known as HIV-1. in 1985, scientists in France identified another closely related virus that also produces AIDS. This virus, named HIV-2, occurs mainly in Africa. HIV-1 occurs throughout the world.
3. People infected with HIV eventually develop symptoms that also may be caused by other, less serious conditions. With HIV infection, however, these symptoms are prolonged and often more severe. They include enlarged lymph glands, tiredness, fever, loss of appetite and weight, diarrhea, yeast infections of the mouth and vagina, and night sweats.
4. An HIV-infected person may develop AIDS from 2 to 15 or more years after becoming infected. In children born with HIV infection, this interval is usually shorter. A few people who have been infected with HIV for more than 15 years have not developed any symptoms or suffer only minor symptoms. An infected person can transmit the virus to another person whether or not symptoms are present. Infection with HIV appears to be lifelong in all who become infected.
5. Researchers have identified three ways in which HIV is transmitted: sexual intercourse, direct contact with infected blood, and transmission from an infected woman to her fetus or baby. The most common way of becoming infected is through intimate sexual contact with an HIV-infected person. In the United States, sexual transmission of HIV has occurred mainly among homosexual men, but it is becoming more frequent among heterosexual men and women.
6. People who inject drugs into their bodies can be exposed to infected blood by sharing hypodermic needles, syringes, or equipment used to prepare drugs for injection. Health-care workers can become infected with HIV by coming into direct contact with infected blood. This may occur through injury with a needle or other sharp instrument used in treating an HIV-infected patient. A few patients have become infected while receiving treatment from an HIV-infected dentist.
7. An infected pregnant woman can transmit the AIDS virus to her fetus even if she has no symptoms. Transmission may also occur from an HIV-infected mother to her baby through breast-feeding.
8. Studies indicate that HIV is not transmitted through air, food, or water, or by insects. No known cases of AIDS have resulted from sharing eating utensils, bathrooms, locker rooms, living space, or classrooms.
A. AIDS viruses fall under two categories that both belong to a group called retroviruses
B. An HIV-infected person may not always develop AIDS
C. Family members should not share eating utensils with an HIV-infected person
D. The symptoms that HIV-infected people develop may be similar to but more severe than those caused by other conditions
E. Of the three ways of HIV transmission indentified by researchers, the most common is through intimate sexual contact with an HIV-infected person
F. An HIV-infected person will always suffer severe symptoms
Paragraph 2 ______.

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答案A

解析 第二段段意为“艾滋病是由两种属于逆转录酶病毒的病毒引发的。”
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