Why does Mr Wang say sorry to Liu Mei

题目

Why does Mr Wang say sorry to Liu Mei
Lin mei is twelve.she is amiddle school student.She is in Class 4,Grade 7.Her teacher is Mr Wang,and Liu Mei's English is not very good.
One day,Mr Mang asks his students to make a sentence with"I'in his English class.He looks at the boys and girls and says,"Liu Mei,it's your turn now."
Liu Mei stands up and says,"I is"Mr Wang stops her and says impatiently"I've told you again and again not to say 'I is'understand?"
"Yes,sir'
"'I' am the ninth letter in the English alphabet,'Liu Mei says in a loud voice.
All the students laugh.Mr Wang's face is red.He says,"I am sorry.I should listen to you completely."
刘梅12岁了.她是一个中学生.she在七年级四班.她的教师是王先生,刘梅的英语不是很好.
一天,王先生在英语课上让学生用“i”造句 .他扫了一遍男孩和女孩说：”刘梅,现在轮到你了“ .
刘梅站起来,并说：“我是”王先生打断了她,并不耐烦地说：“我已经告诉你很多次不能说“i is”懂吗
“是的,先生'
“ ‘i'是英语字母表中第九个字母 .”刘梅用响亮的声音说.
所有的学生哄堂大笑,王先生的脸变红了.他说“对不起,我应该听你把话说全 .

答案

Because Liu Mei's grammar was actually correct, but Mr Wang impatiently interrupted her and modified her grammar.