Twelve healthy volunteers with the Apo–A–IV–1 gene and twelve healthy volunteers who instead have the Apo–A–IV–2 gene...

Ravi on March 12, 2019

@Shiyi-Zhang,

Happy to help.

(C) says, "The bodies of those who have the Apo-A-IV-2 gene excrete
cholesterol when blood cholesterol reaches a certain level."

(C) is incorrect because all we know from the stimulus is that blood
cholesterol levels of those with the Apo-A-IV-2 gene remained the
same, whereas blood cholesterol levels of those with the Apo-A-IV-1
gene rose 20%. We don't have any information on how this happens. For
all we know, maybe their bodies metabolized the cholesterol and
converted it into fatty acids or some other type of biological
substance. We don't have enough support to say that they excreted the
cholesterol.

(E) says, "The presence of the Apo-A-IV-2 gene may inhibit the
elevation of blood cholesterol."

(E) is strongly supported by the information in the stimulus, as the
people in the study with the Apo-A-IV-2 gene were given a
high-cholesterol food but had unchanged blood cholesterol levels. This
suggests that the Apo-A-IV-2 gene may inhibit the elevation of blood
cholesterol. (E) is the correct choice.

Does this make sense? Let us know if you have any other questions!