All parents like to think they can tackle even the hardest questions posed by their offspring.

But every once in a while, children manage to stump even the most knowledgeable of parents.

And now a survey of British parents has compiled a list of the top 10 questions mothers and fathers hate to hear, ranging from the easy, like would a shark beat a dinosaur in a fight? to the tricky, like why is the sky blue? to the near-impossible, such as how much does the earth weigh?

Why is the moon sometimes out in the day? is at the top of the list, and it is one that almost any adult would find hard to answer -- while others are a little more down to earth, such as how do I do long division?

A quarter of parents asked said they found themselves puzzled by their children's science and math questions on a daily basis.

Researchers found that 26 percent of parents think their children are more knowledgeable about math and science than they are, with more than half of parents dreading questions about subjects they cannot answer correctly, leaving them frustrated and embarrassed.

The study found that a third of parents would actively research to find the answers, while many admit they either make up the answers or deflect the question onto their partner.

Polling 2,000 parents with children ages 5-16, it found that many parents believe their youngsters' curiosity for science and math has been fuelled by educational TV programs.