Passage I
Table 1 lists various components of the human immune system and some of their actions. An antigen is a foreign substance that elicits an immune response. An antibody is a molecule that binds specific antigens.
Figures 1 and 2 show the time periods during which cell and/or antibody concentrations are typically above normal during the 28 days after first exposure to an antigen.
Figure 3 shows the stages of infection in humans exposed to the human immunodeficiency virus (HIV), the virus that causes AIDS.
Table 1 and Figure 3 adapted from Neil A. Campbell, Biology, 3rd ed.
©1993 by the Benjamin/Cummings Publishing Company, Inc.
Figure 1 and 2 adapted from Peter H. Raven and George B. Johnson,
Understanding Biology. ©1988 by Times Mirror/Mosby College Publishing.
5. According to Figure 3, after first exposure to HIV, the HIV concentration decreases by the greatest amount during which of the following time periods?
Your Answer is
Correct Answer is B
Explanation
Look at figure 3. HIV concentration decreases by the greatest amount corresponds to the stage where the solid line declines the fastest, that is, the half year-1 year period, so choose B