The invigilator asks "Are there any questions?" The ONLY answer to this question is NO. This is because this question was indirectly open-ended, and when she looks at the exam, she sees that beside Question 1. there is no actual question. Ergo the answer to are there any questions would have to be no, since no questions were asked on the exam.
shareYou're wrong, and your explanation doesn't make sense, because it is literally impossible for the candidates, nor the examiners even, to determine that no questions were asked on the exam, be it on the paper or the rest of the room. Therefore, the correct answer couldn't have been "no", and the "Question 1" bit was to be taken merely as a hint.
The actual exam question is whether anyone had any questions. "Only one answer is required" means there's more than one valid answer. If instead she'd answered "yes", she would still have won. To expand on that, anyone answering "yes" or "no" immediately after he asked "Any questions?" would have fulfilled the requirements of the exam as long as they didn't get disqualified in the duration of the timer.