. In our class, when the bell rang and the teacher closed his book, it was a for everyone to stand up.
A. mark
B. chance
C. signal
D. measure
网友回答
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。