轮子之前有人背水短文★★★★★
点任意英文单词可看释义，弹层里可以「＋ 生词本」把它加入复习。
A long time ago people carried water on their backs in animal skins.
很久以前的人把水装在兽皮里，背在自己背上。
Then somebody put two wheels on a box, and one person could move ten times as much.
后来有人给一个箱子装上两个轮子，一个人就能运十倍的量。
We do not know that person's name, but we use his idea every day.
我们不知道那个人的名字，可他的主意我们每天在用。
A good idea often looks small: a round stone, a stick, a box that stays open.
好主意常常看上去很小：一块圆石头、一根棍、一个不会合上的箱子。