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.
脑 子
“john has a lot of brais.” 一个人只有一个脑袋，怎么约翰会有很多脑袋呢？原来这个词用单数或复数都可以指思维能力。所以having a lot of brains的意思就是“很有头脑”。同样你也可以说“Mary has a good brain”来表示“玛丽很聪明”。
你喜欢数学吗？数学问题有难有易。问题困难的时候，你不得不绞尽脑汁(rack your brains)去寻找答案。不过这对你是有好处的，因为这是锻炼脑子的好方法。
