Which of the following describes the basic anatomical structure of crustaceans?

The correct response highlights that crustaceans possess an exoskeleton composed of chitin and often calcium carbonate. This type of skeleton serves multiple purposes: it provides protection, aids in locomotion, and supports the body structure. The combination of chitin and calcium gives the exoskeleton strength and rigidity, allowing crustaceans such as crabs, lobsters, and shrimp to thrive in diverse marine environments.

In contrast, the other options do not accurately represent the anatomy of crustaceans. The presence of bones is characteristic of vertebrates, not invertebrates like crustaceans. A soft body without a shell describes organisms such as octopuses or worms. Lastly, having a single body segment is typical of some simpler organisms, whereas crustaceans have a more complex body structure divided into distinct segments. Understanding these distinctions is crucial for identifying the anatomical features that define crustaceans.