Which of the following is an example of Crustacea?

Crustacea is a class of arthropods that primarily includes aquatic species, such as crabs, lobsters, shrimp, and some terrestrial forms like pillbugs. Pillbugs, also known as roly-polies or woodlice, are a terrestrial group within the Crustacean class. They have a rigid exoskeleton and are characterized by their segmented bodies, similar to other arthropods, but they possess distinct features such as gills and a two-parted body structure which is typical for crustaceans.

In contrast, spiders belong to the class Arachnida, which encompasses a different group of arthropods characterized by eight legs and no antennae. Millipedes are part of the class Chilopoda and have a cylindrical body and many legs. Mites also belong to Arachnida and share features with spiders, including their eight-legged structure. This distinction highlights why pillbugs are the ideal example of Crustacea, given their classification within that specific class and their shared characteristics with other crustaceans.