blade,
I think there's a misunderstanding here - there aren't three conditions, but only two: "it is healthy to engage in an activity that promotes intellectual development" and "engaging in that activity doesn't detract from social development". With that in mind, the only indicator is "only if", and "only if" has always modified what's right after it. If there is an exception to that rule, I literally have never seen it - I can't think of how it would manifest. So the conditional is as follows:
healthy to engage in an activity that promotes intellectual development
engaging in that activity detracts from social development
Tami,
I'm glad I got to answer your question, because you are 100% right, and that's a sophisticated point. The contrapositive DOES tell you about what's unhealthy! So this principle is, in part, about what's unhealthy. Thus, answer choice (C) is wrong because there's no such misrepresentation at all - it's not a misrepresentation, but a legitimate point that the principle is also about what's unhealthy.
Robert Carroll