多项选择题 What are five of the seven layers that are found in the OSI model?（）

单项选择题 Cisco Technical Support Services portfolio provide customers resources that help ensure that Cisco products operate efficiently, remain highly available, and benefit from up-to-date system software. Is it correct?（）

单项选择题 Which Cisco product is a software component that blocks unwanted connections and provides other gateway security functions for small business?（）