下面这句话怎么解释?
问题描述：
下面这句话怎么解释?
The business of continuing the family lineage and keeping the bloodlines pure is often too important to be left to romance and chance encounters.
句子中to be left.为什么会是to be?
答
be important to do sth.所以用to
be 在这里是被动语态的be：be left