It's like some innate gift passed down through the generations. As sure as the sky is blue, there's a small person out there somewhere asking why the sky is blue.
So what are the questions that every parent dreads? We asked some parents to share theirs to help us put together our guide to some of the worst offenders.
1. Personal probes
Q: "Mummy, why do you have a fuzzy bottom?"
Annie C's five-year-old asked this one day. She then proceeded to "tell everyone at nursery about the phenomenon".
It's bad enough having a pre-schooler point out your wobbly, fuzzy or bald bits, without them broadcasting it to all and sundry. And teenagers wonder why parents always bring out the embarrassing photos when they bring their new partners round. Revenge is a dish best served cold, children.
A: "It’s where I store the emergency fuzzy felt."
2. Anthropomorphic conundrums
Q: "Does the cat ever get bored?"
Is a cat given to ennui? In spite of their considerable freedom, they barely do anything most days, often sleeping for 16 hours at a time. Is that a sign of depression? Given as much freedom, just imagine what a dog would fill its days with!
A: "No, he doesn't get bored. He thinks a spider walking across the floor is the most exciting thing he's ever seen. Yesterday, he watched the rain for over an hour. He's very easily pleased."
[Related feature: What to do if your child cheats]3. Gender brain benders
Q: "Why do boys have willies?" (or "Why don't girls have willies?")
Such a simple question, but how do you answer? Do you go for the straight truth and start drawing biological diagrams? Or do you think of something silly involving cavemen and fire control?
A: "Ask your father."
4. Metaphysical mind-blowers
Q: "What are shadows made of?"
It's probably no surprise to learn that the little boy who asked this grew up to be a writer/illustrator of wacky children's comics about sheep and tiny dinosaurs. Gary Northfield's mum couldn't give an answer, which is nothing to be ashamed of.
A: "The backs of rainbows."
5. Evolutionary mysteries
Q: "Where did the first horse come from?"
Questions like this are the sort you should probably gen up on before your offspring learn to speak. They're a staple part of any child's questioning: things you can actually give a proper answer to if only you'd bothered to get that zoology degree.
A: "Horses evolved about 75 million years ago in Europe and Asia from an animal called Eohippus (Dawn Horse). It was just 60cm (the equivalent of two rulers) in length."
6. Social faux pas
Q: "Is that a man or a woman?"
It's IMPERATIVE that this be asked loudly and within earshot of the person in question in order to cause maximum embarrassment to parents. Popular variants include "Why does that lady have a moustache?" and "Why is that man wearing a dress?".
A: "Shh, darling!"
Q: "How do you make the tap water go hot with your hand?"
This one was asked by a child convinced that the water turned warm only because mum was holding her hand under the tap. Apparently, explanations about boilers and immersion heaters did not pass muster.
A: "I absorb all the cold out of the water. Why do you think my hands are always so cold?"
8. Morbid fascination
Q: "Grandad, when are you going to die?"
This is always a cheery question to ask an elderly relative. Annie C's daughter asked this last time she visited her grandpa. Looks like someone's getting nothing in the will.
A: "When I run out of breaths."
9. Meteorological interrogations
Q: "Why is the sky blue?"
This is another old faithful, and certainly one you can easily learn to answer. How technical you want to get depends on whether you'd like to spend half an hour explaining how the eye sees light of different frequencies as different colours, or if you'd rather use that time to re-grout the bathroom tiles.
A: "The sky appears blue because gas molecules in the atmosphere absorb more blue light and reflect it all around the sky."
Or: "Because that's God's favourite colour."
10. Naked truths
Q: "What's an orgasm?"
These are the questions sent to try us, as Camilla Chafer will attest. Other parents have been asked "What's a prostitute?" "What's a condom?" and "What's a pervert?". They're all words that children might hear as they go out into the world, but wouldn't life be simpler if they didn't?
A: "I'll tell you when you're older" (ah, that old cop out).
Or: If you're feeling brave, you could try a little bit of truth. Not too much, though -- you don't want the playground full of children playing 'prostitutes and peverts'.
What difficult questions have your children asked you? And what did you trouble your parents with as a nipper? Tell us in the comments!
At the heart of Team Mum is the video series Raising an Olympian, sponsored by Proctor and Gamble, profiling athletes from across the world, their dedicated efforts to make it to Olympic Games, and the mothers who had tremendous impacts on their lives. Watch the videos on Yahoo! Lifestyle Team Mum.