In what structure is the arthropod body confined?

The correct answer is the exoskeleton, which is a rigid external covering that provides support and protection for the body of arthropods. This structure is made of a tough substance called chitin, which not only serves as a protective barrier against environmental threats but also plays a crucial role in preventing water loss, an essential feature for survival, especially in terrestrial habitats.

The exoskeleton enables arthropods to maintain their shape and provides a point of attachment for muscles, facilitating movement. During growth, arthropods undergo a process called molting, where they shed their old exoskeleton to allow for the formation of a larger one. This characteristic distinguishes arthropods from other animal groups that possess internal skeletons made of bone or cartilage.

The other choices do not represent the structural confinement of the arthropod body. While endoskeleton refers to an internal skeleton found in vertebrates, cartilage is a flexible connective tissue found in various forms throughout the body, and soft tissue generally denotes tissues that are not hard or rigid, such as muscle and organ tissues. Therefore, the exoskeleton is the defining structure that confines the body of arthropods.