"Idioms About Happy Teacher" Joke

上对外汉语课，老师提问：
“同学们，你们每人说一个汉语成语，形容老师今天很开心很高兴的样子。”
学生很活跃：
“眉开眼笑”
“开怀大笑”
“兴高采烈”……。
老师接着说，
“说出来的成语里要含有数字，
比如一、二、三、四……。”
一位留学生反应很快，大声抢答：
“老师，含笑九泉!”

shàng duìwài hànyǔ kè, lǎoshī tíwèn:
“Tóngxuémen, nǐmen měi rén shuō yīgè hànyǔ chéngyǔ, xíngróng lǎoshī jīntiān hěn kāixīn hěn gāoxìng de yàngzi.” 
Xuéshēng hěn huóyuè:
“Méikāiyǎnxiào”
“kāihuái dà xiào”
“xìnggāocǎiliè”……. 
Lǎoshī jiēzhe shuō,
“shuō chūlái de chéngyǔ lǐ yào hányǒu shùzì, 
bǐrú yī, èr, sān, sì…….” 
Yī wèi liúxuéshēng fǎnyìng hěn kuài, dàshēng qiǎngdá:
“Lǎoshī, hánxiào jiǔquán!”

At a foreign Language class, the teacher asked: 
"Students, each of you say a Chinese idiom describing a teacher who is very happy and cheerful." 
Students are very active: 
"Be all smiles" 
"Laugh a hearty laugh" 
"In great delight" ... 
The teacher then said, 
"In the idiom there should be a number, such as one, two, three, four ...." 
 One student answered quickly and loudly: 
"Teacher, smile in the underworld!"