英文演讲前想来个短笑话缓解一下气氛，请问用什么好呢？

What's the difference between water and ink?!

ans;A drop of ink will tinge a glass of water ,but a glass of water cant tinge a drop of ink.

意思大概就是你问一下水和墨水的分别.那就是一滴墨水能污染整杯清水但是一杯清水不能净化一滴墨水..这应该也能比喻环境吧..