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79. Before there goes the bell for class, our math teacher took out a piece of       and wrote his problems on the blackboard.

79. Before there goes the bell for class, our math teacher took out a piece of       and wrote his problems on the blackboard.

 A.brush pen           B. chalk                   C. paper                     D. Pencil

Before there goes the bell for class, our math teacher took out a piece of　　　 and wrote his problems on the blackboard.

　 A. brush pen　　　 B. chalk　　　 C. paper　　 D. pencil