Why do people wear watches when they cross the desert?
脑筋急转弯最早起源于古代印度。就是指当思维遇到特殊的阻碍时，要很快的离开习惯的思路，从别的方面来思考问题。现在泛指一些不能用通常的思路来回答的的智力问答题。脑筋急转弯分类比较广泛：有益智类，搞笑类，数学类，成人类等。 脑筋急转弯是种娱乐方式，同时也是一种大众化的文字游戏。
1、What is it that is not burnt in the fire, and can't be drowned in the water?
2、I tell heat, and I tell cold, and they in turn tell me to go up and down as I am told. What am I?
3、Why do people wear watches when they cross the desert?
答案：
1、Ice.
2、The mercury in a thermomether.
3、Because watches have springs in them.
