Twelve healthy volunteers with the Apo-A- IV-l gene and twelve healthy

Let's take a look at the whole question to determine why (E) is the correct answer here.

The passage tells us:

• A scientific study was performed
• 12 volunteers with the Apo-A-IV-I gene and 12 volunteers with the Apo-A-IV-2 gene each ate a normal diet supplemented with high-cholesterol food for three weeks
• High cholesterol in the blood is associated with an increased risk of heart disease
• By the end of the study, the blood cholesterol levels of the Apo-A-IV-I group had risen 20%
• However, the blood cholesterol levels of the Apo-A-IV-2 group had remained the same

We're asked to determine which of the answer choices is most strongly supported by this information.

Let's take a look through each of the answer choices in turn. Here's (A):
The study in the passage was split evenly between those with the Apo-A-IV-I gene and those with the Apo-A-IV-2 gene. However, this does not mean that half of the general population has the Apo-A-IV-I gene and the other half has the Apo-A-IV-2 gene.

The information in the passage does not support the suggestion that half the population carries a gene that lowers cholesterol levels. This rules (A) out.

The passage suggests that those with the Apo-A-IV-2 gene may have some protection from a rise in blood cholesterol levels caused by eating a high cholesterol diet. There is no information in the passage about how those already at risk of heart disease may be able to reduce their risk.

(B) is not supported by the information in the passage -- (B) is out.

All we know is that the blood cholesterol level of those with the Apo-A-IV-2 gene had not changed at the end of the three week study. The passage gives us no information on why there had been no change.

We don't know whether these people excrete cholesterol or use some other method to prevent their blood cholesterol levels from rising. (C) is not supported by the information in the passage, so let's cross (C) out.

The passage tells us the blood cholesterol levels of those with the Apo-A-IV-I gene had risen by 20% by the end of the study. We're also told that "A high level of cholesterol in the blood is associated with an increased risk of heart disease."

The information in the passage suggests that, given a high cholesterol diet, those with the Apo-A-IV-I gene have a higher risk of heart disease. This does not support the assertion in (D) that the presence of the Apo-A-IV-I gene "seems to indicate that a person has a lower risk of heart disease."

This means (D) cannot be the answer to this question.

On first reading, you might think this has a similar weakness to (C) -- from the passage we don't know why the blood cholesterol level of those with the Apo-A-IV-2 gene was unchanged at the end of the study.

However, this answer choice tells us the presence of the gene "MAY inhibit the elevation of blood cholesterol." This seems reasonable: we don't know why the blood cholesterol levels of the people with the Apo-A-IV-2 gene were unchanged at the end of the study, but it might be because the gene provides some protection.

The information in the passage does support (E) and since we've crossed out all the other answers, (E) is our answer to this question.

I hope that helps!