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

A. The ip classless command is enabled by default in recent versions of IO
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.