the police ( )looking for the missing boy in the forest

问题描述:

the police ( )looking for the missing boy in the forest
is b.was c.are
d.were
应该选c,但是为什么不选d呢

are
the police 警方,集合名词,用复数为什么不选d?如果用d, 后面会有时间状语 at that time 之类