I think he was serious. The fact that he doesn't know, doesn't make him stupid thoI am not sure. I have already seen a lot of similar questions with the same level of intelligence on ET. Questions that were no jokes.
Remember, we are on ET!

When it comes to questions, -
https://www.elitetrader.com/et/threads/how-long-is-the-intestines-in-our-stomach.366034/