Question

In our class, when the bell rang and the taacher closed his book, it was a        or everyone to stand up

1. A.
   signal
2. B.
   chance
3. C.
   mark
4. D.
   measure

Answer 1

A
signal 信号； chance 机会； mark 记号；measure  措施。句中的it 代替“铃响时教师合上书”这件事，而“它”正是大家要起立的“信号”。