Which of the following is NOT a class 5 animal?

Class 5 animals, in the context of water quality, generally refer to those that are typically found in and around aquatic environments and play a role in the freshwater ecosystem. The correct answer identifies the antelope as not belonging to this class because antelope are terrestrial mammals primarily associated with grasslands and savannas, not aquatic habitats.

In contrast, the other organisms listed—whirligig beetles, water striders, and giant water bugs—are all adapted to living in or around water. Whirligig beetles are known for their ability to skim across the water's surface, while water striders are characterized by their long legs adapted for walking on water. Giant water bugs inhabit freshwater environments and are predatory insects, showcasing the diversity of life that thrives in aquatic ecosystems. Thus, identifying the antelope as the outlier highlights the distinction between terrestrial and aquatic fauna.