lu minger, our physics teacher, is a good teacher. he has been teaching for forty years. we all love and respect him because he has devoted himself to the cause of education.

but he has a very strange temperament①.he often criticizes②us when we make mistakes. so, at first, we couldn't get along well with him;but later, we realized that he was a kind and warm-hearted teacher. we came to love him and looked on him as our good friend.
he is very strict not only with us but also with himself. he will forget his sadness or illness as soon as he stands in front of the blackboard. sometimes he knocks the blackboard heavily to emphasize③ what he is saying. sometimes he laughs or jumps on the platform④. he is absorbed in⑤ teaching and forgets himself. all of us study physics actively and carefully because we have such a good teacher.
mr lu is very old. he will leave the school before long. the number of the students he has taught can't be counted. he has worked all his life for his students, like a candle that burns itself to give light to others.