What are the major functions of the circulatory system?

The major functions of the circulatory system encompass the transport of essential substances throughout the body, making the correct choice focused on transporting hormones, gases, and nutrients. This system, primarily made up of the heart, blood, and blood vessels, facilitates the delivery of oxygen from the lungs to the tissues, the transportation of nutrients from the digestive tract, and the distribution of hormones from various glands. Additionally, it removes carbon dioxide and metabolic wastes, ensuring that all body cells have the necessary materials for energy production and optimal function.

While other options describe important physiological processes, they do not fully encapsulate the comprehensive role of the circulatory system in nutrient and gas exchange. Regulating body temperature and hormone production is more characteristic of the endocrine and thermoregulatory systems, and waste filtration is primarily a function of the renal system. Protection against infections involves the immune system, which works in conjunction with the circulatory system but is not a primary function of it. Thus, the emphasis on transportation in the correct answer highlights the circulatory system's vital role in maintaining homeostasis and supporting life processes.