But doctors say: stay away. "We have no confirmation that anyone has actually done this, but there is certainly lots of chatter on the Internet, and so we know that people are asking these questions,"

VOA: standard.2009.12.18

Because when you make this request "make sure," that the person would either say "Yes, I've done it," or "No, I haven't,"

当你作出“Make sure”的要求时，对方会说，“是的，我已经做了” 或者 “不，我还没做呢。”

Make sure 课堂 - SpeakingMax英语口语达人