Your company has client computers that run Windows 7 and client computers that run Windows XP Professional. You enable the Network Discovery feature on the Windows 7 computers. You discover that the Windows XP computers do not appear on the network map. You need to ensure that all client computers appear on the network map. What should you do?（）

• A、Configure the IPv6 protocol on the Windows 7 computers.
• B、Configure the network shares on the Windows 7 computers to include the user names of all employees.
• C、Configure the network shares on the Windows XP computers to include the user names of all employees.
• D、Install the Link Layer Topology Discovery (LLTD) Responder on the Windows XP computers.