下列短文中有10处语言错误。请在有错误的地方增加、删除或修改某个单词。
增加：在缺词处加一个漏字符号（∧）,并在其下面写出该加的词。
删除：把多余的词用划线（\）划掉。
修改：在错的词下划一横线，并在该词下面写出修改后的词。
注意：
1、每句不超过两个错误；
2、每处错误及其修改均仅限一词；
3、只允许修改10处，多者（从第11处起）不计分。
Mr. Zhou who has been retired is over sixty years old. He is one of my respected teachers. He teaches us chemistry when we were in senior Grade One. He was old, and he taught us well. He tried his best to make his class live. Mr. Zhou usually made good preparations for the lesson and was strict to us, too. Whenever we made mistakes in our homework, he would ask us to correct it. At that time, I was used to be poor in chemistry. Mr. Zhou often helped me with my studies very patiently, as a result of that, I have made rapid progresses and caught up with the class.