维护管理系统包括（）、话务统计子系统、维护子系统、测试子系统和计费处理子系统几部分。
参考答案：数据管理子系统
–I _______ as the manager in this company.
–May I know since when?
A．worked
B．had worked
C．have worked
D．am working
“水火既济”是指心肾两脏的关系。
