知识的“双刃剑”作用（）。

A、有两面性

B、知识就是“宝剑”

C、有利有弊

D、既可以被正义力量应用，也可以被非正义力量利用

In software engineering and systems engineering, (71) is a description of a system's behavior as it responds to a request that originates from outside of that system．

A．black box
B．business rule
C．use case
D．traceability matrix