This question demands analysis at a higher level than simple reading comprehension. In the case of (E) we can see that the author has very deliberately avoided overreaching the evidence to make such a claim. However, in the case of (C), this is a new piece of information we can reasonably infer from the facts presented in the essay, even though it is not explicitly presented itself.
Female-only tournaments exist and many women have gone on to become grandmasters. However, the best players in the world are still considered to be male.
Female-only tournaments exist and many women have gone on to become grandmasters. However, the best players in the world are still considered to be male.
We do have to make some assumptions here. We have to assume that tournament play is what establishes who the "best players" are. Given that assumption however, we can infer that the best players do not play in all-female tournaments, therefore the overall standard of those tournaments is lower (at least if we judge the standard of the tournament by the standard of the best players, rather than by the average level of play, which could conceivably be higher at an all-female tournament, even given what we know).
It's not an airtight case --as you see, it relies on some general knowledge and some assumptions. But it is a reasonable implication. In terms of logical format, the general shape is:
A) No males play at all female tournaments
B) All of the best players are male
Therefore: None of the best players play at all female tournaments.
A) No B are C
B) All A are B
Therefore: No A are C
This is one of the basic syllogism forms (Celarent / EAE-1).
Please note, as always in logic, the structure has nothing to do with the content. We might take issue with (B), the claim that all the best players are male. But if we accept it as presented in the essay, then the conclusion does follow structurally.