Quite a bit of confusion on this one... let's see if we can sort it out.

Read the question stem: Which of the following hypotheses is best supported by the evidence above?

The use of the word 'Hypotheses' signifies that what we are looking for is a proposition that is highly probable in the light of the data given in stimulus.
The stimulus provides evidence (premises) for one of the answer options. So that answer option must be a hypothesis that is supported by the stimulus.

Premises:
- massive doses of vitamin C found that of a group of 600 people who regularly took 1,500 mg of vitamin C daily for a year, fewer than 9 percent suffered serious cases of flu;
- of a group of 600 people who took 250 mg of vitamin C (the standard recommended daily allowance) daily for a year, 34 percent suffered at least one serious case of flu;
- of a group of 600 people who took no vitamin C for a year (other than that found in the foods in a balanced diet), 32 percent suffered at least one serious case of flu.

Let's look at the options to see which one is supported by this data.

(A) The effectiveness of vitamin C in preventing serious cases of flu increases in direct proportion to the amount of vitamin C taken.
Not supported by the study. We do not know how much vitamin C was taken by people who took a balanced diet only. Anyway, we cannot establish the direct proportion.

(B) Vitamin C is helpful in preventing disease.
Too generic. Talks of disease in general. Not supported by the study.

(C) Doses of vitamin C that exceed the standard recommended daily allowance by 500 percent will reduce the incidence of serious cases of flu by 25 percent.
The popular but incorrect option. There is a difference between 'by 25%' and 'by 25 percent points'. If incidence of serious cases of flu was 34% and it reduces to 9%, that is a reduction of (34-9)/34 = 73.5% in the incidence. Or I can say that the incidence of serious flu has reduced by 25 percent points.
Similarly from 5%, if the growth rate goes up to 6%, that is an increase of 1/5 *100 = 20% (not 1%)
But I can say that the growth rate has increased by 1 percent point.

(D) Massive doses of vitamin C can help to prevent serious case of flu.
This is the hypothesis that is best supported by the study. Please note that it is not a 'must be true' statement. The author has already mentioned that these are hypotheses. We need to pick the one that is best supported by the stimulus. It is clear what massive doses are since the premise mentions "studying the effects of massive doses of vitamin C found that of a group...". The results of the study imply that massive doses of vitamin C can help prevent serious case of flu.

(E) A balanced diet contains less than 250 mg of vitamin C.
No information about this. If anything, in the group taking a balanced diet, the incidence of serious flu was slightly less than those taking 250 mg. So if we do want to infer something, we might be tempted to infer (wrongly, let me add) that a balanced diet has more than 250 mg of Vitamin C. We also don't know what kind of diet was taken by people taking 250 mg of Vitamin C.

Answer (D).
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A nutritionist studying the effects of massive doses of vitamin C found that of a group of 600 people who regularly took 1,500 mg of vitamin C daily for a year, fewer than 9 percent suffered serious cases of flu; of a group of 600 people who took 250 mg of vitamin C (the standard recommended daily allowance) daily for a year, 34 percent suffered at least one serious case of flu; and of a group of 600 people who took no vitamin C for a year (other than that found in the foods in a balanced diet), 32 percent suffered at least one serious case of flu.

Which of the following hypotheses is best supported by the evidence above?

(A) The effectiveness of vitamin C in preventing serious cases of flu increases in direct proportion to the amount of vitamin C taken.
(B) Vitamin C is helpful in preventing disease.
(C) Doses of vitamin C that exceed the standard recommended daily allowance by 500 percent will reduce the incidence of serious cases of flu by 25 percent.
(D) Massive doses of vitamin C can help to prevent serious case of flu.
(E) A balanced diet contains less than 250 mg of vitamin C.

D is good

D, though not very sure about it. E may also be considered, I guess.

I wud pick D. The para starts with "A nutritionist studying the effects of massive doses of vitamin C .."

GA

I will go with "B".

Please do POST OA of this question...

Why is C wrong??

This is supported by the argument => Doses of vitamin C that exceed the standard recommended daily allowance by 500 percent will reduce the incidence of serious cases of flu by 25 percent

daily allowance is 250mg. So if this amount is increased by 500 percent, it will be 1500mg. The incidence will be reduced from 34% to 9%.

=> That is correct? Why is not supported?

Thanks.

I would choose D.

I think C is wrong because it says "will reduce the incidence of serious cases of flu by 25 percent", meaning that if we have a total population of x individuals, with the standard recommended daily allowance we have 0.34*x cases of flu. If we reduce this by 25% we have 0.75*0.34*x=22.5% that is a lot more than the 9% in the argument

Well my choice is E. Here goes my reasoning.

Choice D is strong statement to choose. It indicates that Massive doses of vitamin C can help to prevent serious case of flu. Furthermore in the argument it is mentioned that when a group takes 1500 mg of vitamin C, fewer than 9 percent suffered.

Choice B same reasoning too strong statement. Vitamin C is helpful in preventing disease.

Choice A is wrong as in the passage when the people start taking 250 gm of vitamin C, 34 percent suffered at least one serious case of flu.

Choice C is wrong and well explained by ranga.

A) The effectiveness of vitamin C in preventing serious cases of flu increases in direct proportion to the amount of vitamin C taken.

IF more Vitamin C is needed to reduce FLY, than the argument is weakened.

(B) Vitamin C is helpful in preventing disease.

Who cares what do vitamin C do in general ? OUT

(C) Doses of vitamin C that exceed the standard recommended daily allowance by 500 percent will reduce the incidence of serious cases of flu by 25 percent.

and? If they reduce by 25%, 30% or 50%, Who cares?

(D) Massive doses of vitamin C can help to prevent serious case of flu.

IF more vitamin C is needed to prevent serious case of Flu, than it is totaly true, than those who took 1500mg suffered less FLu than the others.
this is the answer

(E) A balanced diet contains less than 250 mg of vitamin C.
and? who cares how much Vitamin C contains a balanced diet ?