What is the 'Do you have any questions?' prompt, and why is it one of the most critical parts of the interview?

It is the closing question in most IB interviews.

1. It shapes the final impression.
2. It tests preparation.
3. It shows whether your interest is specific or generic.
4. It reveals maturity: do you ask about sector, mandates, platform, and growth, or only lifestyle?

Prepare 2-3 questions. At least one should be bank- or sector-specific, one can be role / development-focused, and one can be personal to the banker if appropriate.

'No, I think all my questions were answered.' That wastes one of the best chances to signal interest.