问题：

[单选] Which statement about the ip classless router command is true?（）

A . The ip classless command is enabled by default in recent versions of IOS.
B . The ip classless command should only be enabled when static routing is being used instead of a routing protocol.
C . The ip classless command should be enabled by the network administrator whenever RIPv1 or IGRP is being used.
D . The ip classless command should be enabled by the network administrator whenever OSPF, RIPv2, or EIGRP is being used.