题目内容：
根据下列材料，回答问题。
A student went to college after21all his school examinations. There he put his name down for world geography,22 after the first day, he did not go to 23 any more. The teacher noticed that this student was24absent and thought that he had changed to25class. He was very26when he saw the boy's name on the list of students27wanted to take the geography examination28the end of the year.The teacher had prepared a difficult examination paper, which covered29he had taught,and he was eager to see30this student answered the questions. He expected that his answer would be very31; but when he examined his paper carefully, he found only one small mistake in them.32this surprised him very much, he went through the paper33, but was still not able to find34one mistake, so he sent35the student to question him about his work.
When the student had36the room, the teacher said to him, "I know that you came to my class only once on the first day and that you have been absent from all the others. Yet I have found only one small mistake in your paper.37is that? "
"Oh, I'm sorry about that mistake, sir," answered the student. "After the examination, I realized38I ought to have written. I would not have made that mistake39I had not been confused by your40lecture."
A．having
B．taking
C．passing
D．failing
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