下列哪一项不是环境毒理学在环境因素对健康影响的研究中的优点（）

A.人为地控制化学物的暴露剂量

B.人为地控制化学物的暴露时间

C.更能反映对人的有害效应

D.可应用特殊基因型的细胞、转基因动物等试验材料进行研究

E.效应观察的指标不受限制

A project management technique that is currently in widespread use is the (71) . 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 (72) , which are events that signify the accomplishment or completion of major deliverables during the project. Most system development methodologies also provide (73) , 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. (74) was developed to make clear the interdependence between project tasks before those tasks are scheduled． (75) offers the advantage of clearly showing overlapping tasks.

A．statement of work

B．project planning

C．baseline plan

D．information system planning