How to tell if that drawing the weeb at the back of the class drew is either a base or hentai:

• Does it have nipples?

If not then it's a base.

This scenario has never happened to me before, but I know artists get annoyed when people don't understand that artists don't draw like printers.

Bases don't have uhhh.... details, because it's drawn to get the posing and the atonomy correct.

Hope this helped.