Background: As time passes, the number of HIV copies keeps increasing, while the number of helper T cells keeps decreasing. The graph in Figure below shows how the number of T cells typically declines over a period of many years following the initial HIV infection. As the number of T cells decreases, so does the ability of the immune system to defend the body. As a result, an HIV-infected person develops frequent infections. Medicines can slow down the virus but not get rid of it, so there is no cure at present for HIV infections or AIDS. There also is no vaccine to immunize people against HIV infection, but scientists are working to develop one.

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person had the number of HIV copies increasing as time passed?
Answer: Tom

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person didn't have the number of HIV copies increasing as time passed?
Answer: Nick

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person didn't have the number of helper T cells decreasing?
Answer: Nick

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person had the number of helper T cells decreasing?
Answer: Tom

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person had the ability of the immune system to defend the body decreasing?
Answer: Tom

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person didn't have the ability of the immune system to defend the body decreasing?
Answer: Nick

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person developed frequent infections?
Answer: Tom

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person didn't develop frequent infections?
Answer: Nick

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person had to take medicines to slow down the virus?
Answer: Tom

Situation: A doctor tested two people for HIV. Tom had the virus in his blood, while Nick didn't have HIV, he was healthy. Tom has apparently had the virus for 20 years.

Question: Which person didn't have to take medicines to slow down the virus?
Answer: Nick