The correct answer is option (B). Let us first analyze the passage.
1. Claim of the cereal company:
(Better the education level of people) , (higher likelihood that they ate oatmeal when they were children).
Essentially, the company wants us to believe that oatmeal is beneficial for people. The mechanism: if you had oatmeal as a child, you are somehow set up for a better education than someone who did not have oatmeal.
2. Evidence for the above claim: Random National survey of college graduates
4/5 (80%) of college graduates say that they ate oatmeal at least once a week when they were kids.
What we need to do is strengthen the claim made by the cereal company.
Logic:
The author uses the evidence about college graduates. 4/5 i.e. 80% of them ate oatmeal when they were kids to justify his claim. But what if the same or more proportion of people who did not make it to college also had oatmeal as a child? Then the company's claim would break down.
i.e. what if 4/5 or higher (>=80%) of people who did not make it to college also ate oatmeal when they were young? then can the company still claim that eating oatmeal was beneficial in the manner that it somehow helped one get a better education? if 90% of people who did not make it to college also ate oatmeal, it would weaken our belief that oatmeal was beneficial the way it is claimed.
So, the implicit assumption made by the author is that:
The proportion of people who did not make it to college but ate oatmeal when they were younger is less than 4/5 (<80%). Any option choice that gives evidence to back up this assumption is a strong strengthener for us.
Now, let us look at the option choices:
(A) Four-fifths of all current college graduates eat oatmeal regularly.Irrelevant. The logic of the argument is about whether these graduates ate oatmeal when they were children. Whether they still eat it is irrelevant to the claim we need to strengthen.
(B) Fewer than four-fifths of those without a college degree ate oatmeal regularly when they were children.This is exactly what we arrived at. If this statement is true, then it definitely strengthens our belief in the claim. For example, 80% (4/5) of people who made it to college took oatmeal as kids, while only 40% of people who did not make it to college took oatmeal as kids. This will strengthen our belief that oatmeal is beneficial in some manner to help people get a better education.
(C) Among people who have additional education beyond college, four-fifths ate oatmeal regularly when they were children.Interesting choice. At best, I would consider this a weak strengthener. In our logic, we arrived at an assumption about a group of people not talked about in the passage - people who did not make it to college. This option provides information about yet another group - those who went on and got additional education. The statement says that even in this group, 4/5 (80%) of the people ate oatmeal when they were kids. It does strengthen the argument somewhat as per me. But the problem of the other group remains. Till we can be sure that the group that did not make it to college had less than 4/5 (80%), we cannot definitely say that the claim is true, even if this option was true.
So, it seems to be a weak strengthener at best. Option B is a much stronger strengthener and hence must be the correct choice.
(D) More than four-fifths of the population at large—college graduates and nongraduates combined—ate oatmeal regularly when they were children.This option is also interesting. We need to analyse if this provides any evidence of our assumption/or is in line with our assumption, before we can reject this. if our assumption can be inferred based on this option, then this would also be a correct answer choice.
i.e. can we infer from this option that <4/5 of the people who did not make it to college (i.e. non-graduates) also ate oatmeal as kids?
But, clearly that need not be the case. For example: -
Sample Data 1. Total Population - 100
2. Ate oatmeal - 90 (>4/5)
3. Graduates = 20
4. Non Graduates = 80
5. Graduates who ate oatmeal = 4/5*20 = 16
6. Non graduates who ate oatmeal = 90-16 = 74
7. Non Graduates who ate oatmeal % = 74/80 >90% (i.e. >4/5)
Here, we can see that 1) >4/5 of total population (90/100) ate oatmeal. 2) 4/5 (16/20) of college graduates ate oatmeal. 3. >90% (74/80) of non graduates also ate oatmeal. We can therefore see that we cannot infer out assumption from option D.
So, option D also does not strengthen the company's claim in anyway.
(E) Those college graduates who did not eat oatmeal regularly when they were children did eat oatmeal on an occasional basis.Irrelevant. It does not matter whether oatmeal was eaten frequently or occasionally, it has nothing to do with our claim, which is only about whether oatmeal was eaten or not.
Cheers!