Some of the structures, due to lack of professional planning, construction and maintenance, often have safety problems.

有些构筑物，由于缺乏专业的规划、建造和维护，往往存在安全问题。

And the primary use for that was in the construction and maintenance of intercontinental ballistic missiles.

其主要用途是洲际弹道导弹的建造和维护。

He would spend days at a time helping the family plant and harvest crops or undertake new construction and maintenance projects.

他会花几天时间帮助家人种植和收割庄稼，或者进行新的建设和维护项目。

I think that in order to determine who should pay for the construction and maintenance of a road system, it is very important to look at who ultimately benefits from having it.

我认为， 为了确定谁应该为道路系统的建设和维护付费，非常重要的是要考虑谁最终会从拥有该系统中受益。