A work breakdown structure (WBS) is a tool used to define and group a project's discrete work elements in a way that helps organize and define the total work scope of the project. A WBS is most useful for（）

A.identify ingindividual tasks for a project

B.scheduling the startoftasks

C.scheduling the end oftasks

D.determining potential delays

我国天然气定价机制存在的主要问题包括以下几方面，一是价格水平偏低，与国内供需关系和国际市场价格脱节；二是与石油等替代能源比价关系不合理；三是（）。

A.价格体系和配套政策不健全

B.市场机制建设不健全

C.缺乏政策性干预

D.价格体系不够科学、健全