Which of the following statements about exoskeletons is true?

The statement that exoskeletons are secreted outside the epidermis is accurate and reflects an important characteristic of this type of skeletal structure. Exoskeletons are external skeletons that provide protection and support to the body of an organism. Generally composed of materials such as chitin in insects and calcium carbonate in crustaceans, exoskeletons form a tough and protective layer outside the soft tissues.

This external secretion process is crucial because it allows the organism to maintain its structural integrity while still being able to grow. To accommodate growth, many organisms with exoskeletons undergo a process called molting, where they shed their old exoskeleton to allow a new, larger one to form beneath.

In contrast, the other options do not accurately describe the nature of exoskeletons. Internal structural support primarily characterizes endoskeletons, while exoskeletons are not found in all vertebrates, as vertebrates typically have an internal skeleton. Additionally, exoskeletons are not made of cartilage; instead, they consist of hard substances, unlike the more flexible nature of cartilage found in various organisms with endoskeletons.