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、Why do people never feel hungry on a beach?

2、What's the difference between a monkey and a flea?

3、What hangs on the wall without nail or string?

答案：

1、Because of the sand which is there

2、A monkey can have fleas but a flea cannot have monkeys

3、Cobweb