joke

我们的老师经常以一个有趣的笑话开始上课。

Our teacher often starts the class with a funny ___joke.

这是个严肃的问题，所以请不要拿它开玩笑。

This is a serious matter, so please don't ___joke about it.

这是个敏感话题，所以请不要拿它开玩笑。

This is a sensitive topic, so please don't ___joke about it.