1) Psychological research indicates that college hockey and football players are more quickly moved to hostility and aggression than are college athletes in noncontact sports such as swimming.

2) But the researchers’ conclusion—that contact sports encourage and teach participants to be hostile and aggressive—is untenable.

3) The football and hockey players were probably more hostile and aggressive to start with than the swimmers.

Which of the following, if true, would most strengthen the conclusion drawn by the psychological researchers?

(A) The football and hockey players became more hostile and aggressive during the season and remained so during the off-season, whereas there was no increase in aggressiveness among the swimmers.
- If this was true, then the researchers are right. The contact sports made hte players hostile and they continued that hostility even in off season.

(B) The football and hockey players, but not the swimmers, were aware at the start of the experiment that they were being tested for aggressiveness.
- Not important.

(C) The same psychological research indicated that the football and hockey players had a great respect for cooperation and team play, whereas the swimmers were most concerned with excelling as individual competitors.
- Not important.

(D) The research studies were designed to include no college athletes who participated in both contact and noncontact sports.
- Would call the study in question, since it makes a conclusion for college athletes playing contact/non contact sports

(E) Throughout the United States, more incidents of fan violence occur at baseball games than occur at hockey or football games.
- Not concerned with fan's reactions

I'll go with A

conclusion: players themselves are more hostile and aggresive not they are hostile and agreesive because of the contact sports such as football and hocky.

(A) The football and hockey players became more hostile and aggressive during the season and remained so during the off-season, whereas there was no increase in aggressiveness among the swimmers
=> it is exactly waht the conclusion is.
(B) their testing of aggressiveness is irrelavant.
(C) it actually weakens the conclusion.
(D) irralavant.
(E) we have nothing to do with the case of a particular country like United States and fan violence.

A looks like it

I was confused by this statement

But the researchers’ conclusion—that contact sports encourage and teach participants to be hostile and aggressive—is untenable

When I first read it, I assumed it meant that the researchers's thought that the conclusion that contact sports teach hostility is untenable. Therfore, I had trouble accepting the OA.

After reading it multiple times, the meaning became clear. A is definitely the correct answer