The police had been told that a bomb had been planted on the plane.

问题描述:

The police had been told that a bomb had been planted on the plane.
我认为前面应该用过去时,后面用过去完成时,为什么前后都用过去完成时

假设这么一个情况:
警察什么都没做,炸弹爆炸了.事后一人埋怨道:
The police had been told that a bomb had been planted on the plane.
警察已经被告知.(但他们什么都没做)