我们先来看一个故事，来猜猜文章中和人身体有关的短语的含义吧。

Last year my English class was full of characters. That's a polite way of saying it had some unusual people that I'll never forget. One student was such a hard worker that he learned all the idioms in our book by heart. He was always saying things like "I'm on cloud nine", or "I'm green with envy". We never knew if he meant what he said or if he was just practicing English. Another student had a sweet tooth. She would bake lots of bread and cakes and bring them to every class for us to share during breaks. Two students met in the class and fell head over heels in love. We were all invited to their wedding and had a great time. Then there was a student who was always pulling someone's leg. For example, one day before class, he put a long homework assignment on the board and made us think that the teacher had given it. We all had long faces until the teacher came in. Then we realized that someone had played a joke on us.

现在看看这些成语在例句中的用法，你能猜出它们的含义吗？

by heart     
I know all my friends' telephone numbers by heart. I never have to look in the telephone book.
含义是是熟记，背诵

have a sweet tooth     
I know you have a sweet tooth, so I bought you a box of chocolates.
含义是爱吃甜食

head over heels in love     
Pam and Tony are head over heels in love. They're planning to get married.
含义是深爱着某人

pull someone's leg     
Tomorrow is not a holiday. Don't believe Rich. He's just pulling your leg.
在口语中，含义是愚弄某人，开某人的玩笑

a long face     
Because Judy didn't get an invitation to the party, she's walked around with a long face since yesterday.
这可不是说人脸拉的跟长白山似的，这个短语的意思是郁闷（忧虑）的表情，愁眉苦脸

这段话的意思就是：

去年我英语课的班级里全是人物。这是一种礼貌的说法来表达班级里有一些我永远不会忘记的不寻常的人。一个同学非常努力把我们书上所有的短语都背下来了。他说话总是像这样，“我飘飘欲仙了”，或者“我妒火中烧”。我们总是不知道他是说真的还是只是练习英语。还有一个同学爱吃甜食，她总是烤很多面包和蛋糕，带到班级里在每一堂课的课间跟我们分享。两个同学在班级里一见钟情坠入爱河，我们都被请去参加他们的婚礼，非常开心。还有一个同学喜欢开玩笑。比如有一天上课之前，他在黑板上写了好多好多作业并且让我们以为是老师留的，我们都愁眉苦脸的直到老师走进教室，然后我们才发现是有人跟我们开了一个玩笑。