（）是一种系统需求，描述了与用户相关的操作特征。
A.技术需求
B.性能需求
C.可用性需求
D.可靠性需求
参考答案：C
— Did you happen to see _______ black and _______ white cat?
— Are they missing? I told you to take care of them.
A．a; 不填
B．the; 不填
C．the; the
D．a; the
人工创造的品种资源
