The correct answer is option 3In classful addressing, once a network id is assigned to an organization, there is no method available to allocate the unused IP addresses of that network to other organizations. Hence a large part of the available addresses is wasted.Additional InformationTo overcome this wastage CIDR blocking scheme is developed.In this scheme, a network can be formed in chunks of IP addresses required and can be used by different organizations.Subnets can also be formed within the network block.Classful addressing schemeClassLeading bits (Reserved)Network ID (bits)Number of NetworksHost ID (bits)Start AddressEnd AddressClass A0827240.0.0.0127.255.255.255Class B101621416128.0.0.0191.255.255.255Class C110242218192.0.0.0223.255.255.255Class D1110Not DefinedNot DefinedNot Defined224.0.0.0239.255.255.255Class E1111Not DefinedNot DefinedNot Defined240.0.0.0255.255.255.255