elias.latour.apex wrote:Thank you for posting this question.

When we start doing a sentence correction problem, we should read carefully for the meaning. The sentence seems to say:

It has been demonstrated (present tense)
that individuals who participated in competitive sports (past tense)
when they are in college, tend [to remain](present tense)
physically active in their later years.

The problem with the underlined sentence is two fold. First, the present tense doesn't go well with the verb participated that goes ahead of it. It seems that the best verb to refer to the sports they participated in in the past is were. Accordingly, we eliminate (A) and (D).

Now that we have three candidate sentences, we can look for the differences among them. (E) is the worst of the three, not only because the verb were is suspect (as it seems to refer not to the past but rather to a situation later in the lives of people who go to college) but also because the word liable is unclear and potentially confusing.

So now we are down to (B) and (C). The phrases likely to be and apt to be mean the same thing, so we can ignore that. The real difference between the two sentences is the verb tense (are vs. were). Do you think that we are talking about the past (people who, for example, have died) or about the present (making a generalization about the later-in-life habits of people who did competitive sports in college)?

While there's nothing inherently wrong with the grammar in sentence (C), it does not express the meaning that we find in the original sentence in the best way possible. Accordingly, (B) is the best answer.