The President was talking to all the department heads while a group of unexpected important clients had arrived for a talk with him.

A．when ... were arriving

B．as ... had arrived

C．when ... arriving

D．when ... arrived

目标管理的具体做法分三个阶段：第一阶段为目标的设置；第二阶段为实现目标过程的管理；第三阶段为测定与评价所取得的成果。