Day after day 日复一日
A teacher was always so involved in the text being studied that he never looked up .
He would call on a student for translation and explanation, and-without realizing it-he often chose the same student day after day. Out of respect, the student wouldn't point this out to him.
After being called on four days in a row, a student named Goldberg asked advice from his friends. The next day when the teacher said "Goldberg, translate and explain," Goldberg replied, "Goldberg is absent today."
"All right," said the teacher. "You translate and explain."