Final answer:
The correct statement about variable-length subnet masking is that the size of each subnet can be different based on the specific requirements. This technique provides efficiency in IP address allocation and network structure.
Step-by-step explanation:
The statement that is true about variable-length subnet masking is: 2) The size of each subnet may be different, depending on requirements. Variable-length subnet masking (VLSM) allows a network administrator to divide an IP network into subnets of different sizes, unlike traditional subnetting which divides networks into subnets of equal size. With VLSM, you can 'borrow' bits from the host portion of the IP address to create subnets of varying sizes. This method is more efficient because it can minimize wasted IP addresses, allowing for more precise allocation based on the actual number of hosts required in each subnet.
Thus, VLSM offers the flexibility to create smaller or larger subnets to fit the specific needs of different network segments, providing an efficient way to conserve IP addresses and structure a network hierarchically.