Respond and ask.

Our military psychologist used this question to intimidate conscripts. Actually, no, he asked why grass is green. I explained to him in detail about chlorophyll (or whatever it's called, I've forgotten, I knew it in school), and then, when he was already preparing to escape from me, I refuted my own theory by telling him that our color perception depends only on the ability of objects to reflect and absorb waves of a certain length (frequency). I think he liked it; he had a happy, expressionless face. :)

Why can't people fly like birds?