Which class of IP addresses is designated as experimental?

The class of IP addresses designated as experimental is Class E. This class includes IP addresses in the range of 240.0.0.0 to 255.255.255.255. Class E addresses are reserved for experimental and future use, primarily intended for research purposes. This means that they are not used for standard network operations or for public use, which differentiates them from other classes that are designated for specific purposes, such as unicast or multicast addressing.

Class A, Class B, and Class C are used for different sizes of networks, providing a range of addresses for various applications in standard networking, while Class D is specifically used for multicast groups. Therefore, Class E’s unique status as experimental makes it the correct answer.