Final answer:
Crustaceans are arthropods known for their aquatic dominance and distinctive physical features like two pairs of antennae, mandibles. The correct answer is option d).
Step-by-step explanation:
Crustaceans are a diverse group of arthropods that include crabs, lobsters, shrimp, krill, and woodlice. Unlike mollusks, arachnids, and insects, crustaceans are unique in their two pairs of antennae, mandibles for mouthparts, and primarily biramous appendages which are characteristic of this group.
They include species like crabs, lobster, and shrimp, and have a wide variety of adaptations that suit them to both aquatic and terrestrial environments. They posses an exoskeleton that may be bound together, such as in the carapace, which protects their gills and serves as a defense mechanism.
Additionally, they have a straight tube digestive system with a gastric mill, and they must periodically shed their exoskeleton to grow, known as molting. With approximately 70,000 described species, crustaceans are the most dominant aquatic arthropods, although some species such as woodlice have adapted to terrestrial life.