. In our class when the bell rang and the teacher closed his book it was afor everyone t

问题补充：

. In our class, when the bell rang and the teacher closed his book, it was afor everyone to stand up.

A. mark

B. chance

C. signal

D. measure

答案：

A. mark

B. chance

(答案→)C. signal

D. measure

解析：词义辨析。mark标志，符号；chance机会，运气；signal信号，暗号；measure测量；尺寸。句意：在我们班的，当铃声响时，老师合上他的书，这对于每个人来说是一个起立的信号。故选C。