Final answer:
The number of possible subnet masks for three subnets depends on the class of the network and the structure of network needs. Without specific details, we cannot provide an exact number, but with a class C network, for example, several common subnet masks could be used based on how many hosts are required per subnet.
Step-by-step explanation:
The student asked about the number of possible subnet masks for three subnets. Subnets require a unique subnet mask to define the range of IP addresses within that subnet. The number of possible subnet masks is determined by the number of bits used for the subnet portion of the IP address, which varies depending on the class of the network and how the network is divided.
However, the question as stated doesn't provide enough information to give a specific number because it depends on the class of IP addresses being used (A, B, or C) and how the network needs are structured. Generally, with class C networks, you often see subnet masks like 255.255.255.0, 255.255.255.128, 255.255.255.192, etc., which are common for small subnets.
For example, if a class C network is being used and each subnet needs to support at least 30 hosts, the subnet mask could be 255.255.255.224, which allows for 32 addresses (30 usable addresses plus network and broadcast address). For this scenario, the number of subnets would be determined by how many bits you borrow from the host part of the address to create these subnets.