A customer uses an IBM xSeries x366 for their network server.They experienced downtime when the NIC failed earlier this year.Their Novell 6.5 server needs to be accessible all the time at the highest speed possible.Slots are available where network adapters can still be added. High availability is the primary requirement， but increased network bandwidth on the server is also required. Which of the following is the most cost-effective solution to satisfy all of the customer’s requirements？（）

A. Upgrade the network switches to 10Gb speed.
B. Install a dual port gigabit Ethernet adapter and configure adapter load balancing teaming with the onboard adapters.
C. Install one extra adapter to team with the internal adapter and configure adapter failover.
D. Install two additional NICs and configure adapter load balancing teaming with the onboard adapters.