The correct answer is B. FALSE.
There are 100 people at the party, and we know that 50 of them are wearing pink and 50 are not. We also know that 50 of the people are men and 50 are women. If a pink-wearing guest leaves, we cannot say for certain whether it was a man or a woman. It is possible that it was a man, but it is also possible that it was a woman.
The answer A is incorrect because it states that the pink-wearing guest who left was a man. However, we cannot say for certain whether this is the case.
The answer B is correct because it states that we cannot say for certain whether the pink-wearing guest who left was a man or a woman. This is the only answer that is consistent with the information that we have been given.