对于活动应该进行资源平衡(Resource Leveling)

The population is leveling _______ in the area as a result of family planning. A: with B: off C: up D: against

Which of the following statements is true?( ) A: The other three options all meet the requirements B: Leveling refers to leveling the surface of ore retention pile after local ore releasing. C: Prying roof means that the roof and two sides of loose ore rock should be pryed off when the site is leveled. D: Gravity ore drawing is generally adopted for local ore releasing