2. brain
“John has a lot of brains.” A person has only one brain. How come john has a lot of brains? The word, either in the singular or in the pjural form, can mean the ability to think. So ghaving a lot of brains means” being very intellignet” Similarly, you can say “ Mary has a good brain” to mean “ Mary is intelligent”.
Do you like mathematics” Problems in mathematics may or may not be easy. When they are difficult. You have to rqack your brains to get the answers. But this is good for you because it is a good way to exercise your brain.
腦 子
“john has a lot of brais.” 一個人只有一個腦袋，怎么約翰會有很多腦袋呢？原來這個詞用單數或復數都可以指思維能力。所以having a lot of brains的意思就是“很有頭腦”。同樣你也可以說“Mary has a good brain”來表示“瑪麗很聰明”。
你喜歡數學嗎？數學問題有難有易。問題困難的時候，你不得不絞盡腦汁(rack your brains)去尋找答案。不過這對你是有好處的，因為這是鍛煉腦子的好方法。
