“This question” means “the current question being g asked” and trying to argue otherwise is just silly. The only way you could be confused in that is if you’re not a native English speaker (and if you’re not, fair enough). My point being, you are given the full question, the question being referenced, and the possible answers.
It’s unanswerable not because of a language error, it’s because the second 25% makes it impossible to correctly answer as the answer is essentially a mathematical paradox. All answers are simultaneously correct and incorrect.