虚拟语气中should什么时候可以省略?

问题描述:

虚拟语气中should什么时候可以省略?
The mad man was put in the soft-padded cell lest he _____________ himself.
A) injure B) had injured C) injured D) would injure
上题,我认为划线处应该填入should/would be injured.但是答案是C.怎么省的?should be都省了?
没有省略

没有省略