What's an example of a "dumb" question that a youngster might ask?

The kid isn’t dumb, just curious and busy learning. But he or she has to bear heaps of scorn anyway from an older sibling who already knows the answers.

What’s the question?

I am looking for realistic examples of questions that a young child might innocently ask and that the older brother or sister might ridicule, calling them dumb. My kids are long past those ages. I am drawing a blank and can’t think of any (or find them online, unless they are about sex or God or unmitigated cuteness). I need this to illustrate something.