A project management technique that is currently in widespread use is the (27) . The purpose of this technique is to detail, in hierarchical fashion, all of the activities that are required to meet project objectives. There are some special activities called (28) , which are events that signify the accomplishment or completion of major deliverables during the project. Most system development methodologies also provide (29) , whose purpose is to contain the various pieces of relevant information - feasibility assessments, schedules, needs analysis, and so forth - in a single place so that they can be presented to project clients and other related parties. Several types of important network diagrams are used in project management. (30) was developed to make clear the interdependence between project tasks before those tasks are scheduled. (31) offers the advantage of dearly showing overlapping tasks.

27（）

A. Functional decomposition diagram

B. Work Breakdown Structure

C. Structure Chart

D. Organizational Structure

用洗油吸收煤气中的苯时，为什么说油温度保持比煤气温度略高几度？