Which of the following arthropods have at least 5 pairs of legs and breathe by means of gills?

The correct choice is based on the defining characteristics of crustaceans. Crustaceans are a sub-group of arthropods that typically have a minimum of 5 pairs of legs, which includes species such as crabs, lobsters, and shrimp. They breathe through gills, a specialized respiratory system that allows them to extract oxygen from water. This gill structure is essential for their survival in aquatic environments.

Insects do not have gills and have a different respiratory system that relies on spiracles and a tracheal system. Araneae, which are spiders, belong to a different class of arthropods (Arachnida) and also do not possess gills, as they breathe through book lungs or trachea. Myriapoda, which includes centipedes and millipedes, have numerous legs but lack gills; instead, they generally respire through the entire body surface or via tracheae.

Understanding these distinctions helps clarify why crustaceans are the only group listed that fits the criteria of having at least 5 pairs of legs and utilizing gills for breathing.