开放系统互连（OSI）（）中的第一层为物理层。
A.实际模型
B.测试模型
C.参考模型
D.模型
参考答案：C
（75） involves comparing actual or planned project practices to those of other projects to generate ideas for improvement and to provide a basis by which to measure performance. These other projects can be within the performing organization or outside of it, and can be within the same or in another application area.
A．Metrics
B．Measurement
C．Benchmarking
D．Baseline
故障处理是嵌入式系统架构过程中需要重点关注的内容之一。通常情况下，嵌入式系统故障分为硬件故障、应用软件故障和操作系统故障3类。硬件故障一般不包括______。
A．CPU资源枯竭 B．存储器访问错误C．定时器计数错误 D．MMU配置错误
