A survey from the U.K. involving 1,000 mothers found that moms may be the most quizzed people on the planet. On average, from breakfast to afternoon tea time (remember this was in the U.K.) the average stay-at-home mom faces one question every two minutes and 36 seconds. That adds up to about 105,120 questions per year.

The questions spike during meal times. Girls aged four are the most curious, asking an incredible 390 questions per day. On the other end of the spectrum, boys aged nine ask the least amount of questions. According to the survey, the moms claimed that these were the top five toughest questions (in order):

1. Why is water wet?
2. Where does the sky end?
3. What are shadows made of?
4. Why is the sky blue?
5. How do fish breathe under water?