题目内容：
阅读下列短文，回答题。"Who has more questions,a teacher or a student?" A great learned man told his student that the answer to this question was that a teacher has more questions.
The student became a little puzzled. With a smile,the teacher drew two circles. Within the larger circle is my knowledge of things, and within the smaller one is yours. Outside of the circles is knowledge still unknown to both of us. As you can see my circle is larger, the line that marks out the circle is longer. That makes it clear who has more chances to face something still unknown.
The great learned man believed that__________. A．a teacher has more questions
B．a student has more questions
C．both a teacher and a student have questions
D．everyone,except a teacher,has more questions
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