Melinda French Gates' former chief of staff, who cofounded a unicorn startup, says 'Do you have any questions?' is the most important interview question to nail. Here's how to answer it.

• Jeffrey Spector is the cofounder of Karat and the former chief of staff to Melinda French Gates.
• He says applicants should be more thoughtful when answering, "Do you have any questions for me?"
• His top interviewing tip is to knock the "question" question out of the park.

At the tail end of almost every job interview, when you're probably relieved that it's over, the person across from you asks, "Do you have any questions for me?"