On Cisco Nexus 5000 Series Switches， where are the virtual output queues implemented， and what is the main purpose of virtual output queues？（）

• A、 on all ingress interfaces； to ensure maximum throughput on a per-egress， per-CoS basis
• B、 on all ingress interfaces； to provide independent congestion management and 16 queues
• C、 on all egress interfaces； so that a congested egress port does not affect traffic directed to other egress ports
• D、 on all egress interfaces； to prevent head-of-line blocking by utilizing multiple virtual output queues
• E、 on all egress interfaces； to be able to use EEE 802.1p CoS