Critical Reasoning

A person's dietary consumption of cholesterol and fat is one of the most important factors determining the level of cholesterol in the person's blood (serum cholesterol). Serum cholesterol levels rise proportionally to increased cholesterol and fat consumption until that consumption reaches a threshold, but once consumption of these substances exceeds that threshold, serum cholesterol levels rise only gradually, even with dramatic increases in consumption. The threshold is one fourth the consumption level of cholesterol and fat in today's average North American diet.
The statements above, if true, most strongly support which one of the following?
(A) The threshold can be lowered by lowering the dietary consumption of cholesterol and fat.
(B) People who consume an average North American diet cannot increase their consumption of cholesterol and fat without dramatically increasing their serum cholesterol levels.
(C) People who consume half as much cholesterol and fat as in the average North American diet will not necessarily have half the average serum cholesterol level.
(D) Serum cholesterol levels cannot be affected by nondietary modifications in behavior by nondietary modifications in behavior, such as exercising more or smoking less.
(E) People who consume less cholesterol and fat than the threshold cannot reduce their serum cholesterol levels.

is it a must be true type question
pls explain the answer

would go for C.

A)out of scope. we do not know how threshold can be lowered.

B)contradicts the information in the passage

D)out of scope. no mention about non-dietary modifications in the passage

E)contradicts the information in the passage. below the threshold, serum cholesterol is proportional to the cholesterol consumption

yes, its an inference type/must be true type question.

thephoenix wrote:A person's dietary consumption of cholesterol and fat is one of the most important factors determining the level of cholesterol in the person's blood (serum cholesterol). Serum cholesterol levels rise proportionally to increased cholesterol and fat consumption until that consumption reaches a threshold, but once consumption of these substances exceeds that threshold, serum cholesterol levels rise only gradually, even with dramatic increases in consumption. The threshold is one fourth the consumption level of cholesterol and fat in today's average North American diet.
The statements above, if true, most strongly support which one of the following?
(A) The threshold can be lowered by lowering the dietary consumption of cholesterol and fat.
(B) People who consume an average North American diet cannot increase their consumption of cholesterol and fat without dramatically increasing their serum cholesterol levels.
(C) People who consume half as much cholesterol and fat as in the average North American diet will not necessarily have half the average serum cholesterol level.
(D) Serum cholesterol levels cannot be affected by nondietary modifications in behavior by nondietary modifications in behavior, such as exercising more or smoking less.
(E) People who consume less cholesterol and fat than the threshold cannot reduce their serum cholesterol levels.

is it a must be true type question
pls explain the answer

IMO C
serum cholestrol level rises proportionately to increased cholesterol and fat consumption until the consumption reaches the threshold and the threshold is one fourth the consumption level of cholesterol and fat.

Since the consumption is more than one fourth(ie half) in option C, serum cholesterol level will not raise propertionately beyond one fourth the average North American diet. Therefore people may not necessarily have half the average serum cholesterol level.

Please post the OA. I think it's D.

If it's not [spoiler]'D'[/spoiler], then why not?

paddle_sweep wrote:Please post the OA. I think it's D.

If it's not [spoiler]'D'[/spoiler], then why not?

IMO C is the answer.
D is out of scope. There was no mention of nondietary modifications in the statement.

I was down to B or C but B can't be right because a substantial increase in consumption of cholesterol and fat should result in a substantial increase in cholesterol levels if they are proportional and below the threshold.

I would go C.

The correct answer is something that must be true. Thus, the four wrong answers could or must be false.

Let's look at the choices:

(A) The threshold can be lowered by lowering the dietary consumption of cholesterol and fat.

This must be false based on the definition of "threshold". Also, the threshold is given as one fourth the consumption level of cholesterol and fat in today's average North American diet. Since the consumption level of cholesterol and fat in today's average North American diet is a constant (at least until tomorrow!), the threshold iteslf is a constant. So, the passage also proves that this choice must be false. Eliminate.

(B) People who consume an average North American diet cannot increase their consumption of cholesterol and fat without dramatically increasing their serum cholesterol levels.

Yes they can. Once the threshold is exceeded serum cholesterol rises only gradually, even with dramatic increases in consumption. This choice must be false. Eliminate.

(C) People who consume half as much cholesterol and fat as in the average North American diet will not necessarily have half the average serum cholesterol level.

This must be true. We know from the passage that serum cholesterol rises rapidly until the threshol is met, and thereafter will increase only gradually, even with dramatic increases in consumption. Also, we know from the passage that the threshold is one-fourth th level of cholesterol and fat in the average North American diet. So, people who are eating half that amount are still well past that threshold. So, their serum cholesterol will be really high, and if they were to increase their consumption of cholesterol and fat to the average North American level their serum cholesterol will rise only gradually.

*Note that on test day, we should stop here and select this choice.*

(D) Serum cholesterol levels cannot be affected by nondietary modifications in behavior by nondietary modifications in behavior, such as exercising more or smoking less.

This is outside the scope, and so this choice could be false.

(E) People who consume less cholesterol and fat than the threshold cannot reduce their serum cholesterol levels.

The passage tells us that serum levels rise proportionally with cholesterol/fat intake until threshold is reachd. So, even if you are below threshold, you can reduce your serum levels by reducing your intake. Hence, this choice must be false.