问题补充:
In our class, when the bell rang and the teacher closed his book, it was a for everyone to stand up.
A. signal
B. chance
C. mark
D. measure
答案:
(答案→)A. signal
B. chance
C. mark
D. measure
解析:signal信号;chance机会;mark标志;measure测量。句意是在我们课堂上,当铃声响起,老师合起课本时,这是让每个人都起立的信号。故选A。