问题
选择题
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
A.
考查名词。根据句意可知打铃及老师合上书本，这是下课的暗示，选项中只能选择signal。chance“机会”，mark“分数，痕迹”，measure“方法，措施”。