Number of subnet are 2^n-2 n->subnet network bits
Number of host per are 2^m-2 m->host bits
Number of subnet=2^8-2=254(1 to 254 )
Number of host=2^8-2=254(1 to 254 )
network mask(network bits and sub network bits are 1's and host bits are 0)
=>255.255.255.0(B option)