I had no idea what QE was at the time, I immediately thought of quarterly earnings, but you can't simply comment on QE without having a company to comment on. It turned out that the interviewer was speaking of Quantitative Easing. The best thing you can do when you're faced with a question you don't know the answer is to just be honest. Say you're not familiar with it and ask if you can look into it and provide some insight on it as soon as you do, after the interview, via e-mail.