What's a question or problem that requires a bit of thought before you answer? It's a riddle, of course. The verb riddle can mean to speak in a puzzling fashion, though that use is not very common.
The word riddle might put you in mind of such brain-teasers as "Why did the chicken cross the road?", but riddles actually have a distinguished history in English literature going back to the 10th century. Today, you often find riddle used to mean a hard problem or question to figure out. Is it a riddle to you why you have to go to school? In an unrelated use, if something is riddled with holes, there are many holes in it, quite possibly from bullets!