The back of the Class

Why is the IPv4 address range of not considered part of a subnet class?

A) The 127 network is used only for government and military use

B) The 127 network is not included in most TCP/IP stacks

C) The 127 network cannot be clearly delineated with binary mathematics (it’s a prime number)

D) The 127 network contains reserved addresses

E) Subnet classes are an antiquated descriptor of address segmentation