What is the main function of the skeletal system?

The primary function of the skeletal system is providing structural support to the body. It acts as a framework that supports the body's shape and enables movement by serving as attachment points for muscles. The skeletal system also protects vital organs, such as the brain, heart, and lungs, by encasing them in bony structures. Additionally, it plays a critical role in the production of blood cells within the bone marrow and serves as a reservoir for minerals like calcium and phosphorus, which are essential for various physiological processes.

The other options focus on functions carried out by different systems in the body. For instance, regulating hormone levels pertains to the endocrine system, facilitating digestion is associated with the digestive system, and producing antibodies is a function of the immune system. Each of these utilizes different organs and processes that are distinct from the mechanical and structural roles played by the skeletal system.