单项选择题
A.Allow a CSS to probe the server B.Allow a connection to be closed with a TCP RESET C.Allow persistent connections D.Allow the use of HTTP HEAD request
A.Addition or Deletion of PVC B.PVC status （active or inactive） C.Link integrity D.None of the other alternatives apply
A.It provides comprehensive Domain Name system B.It provides DHCP administrative functionality C.It provides TFTP server functionality. D.All of the above are true