Actually, I may have figured it out haha. I see it as the conclusion is saying that the correlation between the powers gained from playing chess and achievement in other areas of intellectual activity in fact implies that playing chess caused these achievements. And C wrecks that by saying that in fact, having intellectual achievement (ie high gpa) was required for joining the chess team. Am I correct on this? Any comments would be appreciated.
The conclusion of the argument is that the chess program contributed to the students' academic achievement in other areas because through playing chess they exercised spatial reasoning, etc.
C undermines it by implying that many of the students who completed the chess program saw improved academic achievement because after doing the program they wanted to be on the chess team. In order to be on the chess team, they had to have a high GPA, so maybe they just put in more effort. C is right because it offers an alternative reason for their improved academic performance.
D doesn't have much to do with the argument. It's about students who didn't participate in the program so it doesn't weaken it as it's not even about the group of students the argument addresses.
Comments
I don't have that test in front of me but C sounds like your standard weakening AC for cause/effect
C undermines it by implying that many of the students who completed the chess program saw improved academic achievement because after doing the program they wanted to be on the chess team. In order to be on the chess team, they had to have a high GPA, so maybe they just put in more effort. C is right because it offers an alternative reason for their improved academic performance.
D doesn't have much to do with the argument. It's about students who didn't participate in the program so it doesn't weaken it as it's not even about the group of students the argument addresses.