听力原文： Ten graduate students who have served as teaching assistants this year have been nominated to receive awards for outstanding teaching. They were chosen from out of approximately 500 teaching assistants. There will be a ceremony on Tuesday evening at 7:30 to honor them. The chancellor will present each of the winners with a cash prize of ＄100 and a certificate commending them. The chancellor has noted that teaching assistants are an integral part of our campus, and that the quality of undergraduate education has been improved by the quality of our teaching assistants. They work long hours leading discussion groups, grading papers, and overseeing lab work. Most of them work as teaching assistants to help with the cost of their education. Please come to the ceremony on Tuesday to show your appreciation of these hard-working students.
(23)

A. 500.
B. 100
C. 10.
D. 7