Which of the following components is part of the circulatory system?

The circulatory system is primarily responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body. The heart, blood, and blood vessels form the essential components of this system. The heart acts as the pump that circulates blood; blood is the fluid that carries oxygen and nutrients to tissues and returns waste products to the organs responsible for elimination; and blood vessels, including arteries, veins, and capillaries, are the pathways through which blood flows.

The other components listed in the options relate to different systems in the body. For instance, the lungs, trachea, and diaphragm are part of the respiratory system, which is involved in gas exchange. The brain, spinal cord, and nerves constitute the central and peripheral nervous systems responsible for transmitting signals and processing information. Lastly, the stomach, intestines, and liver belong to the digestive system, which breaks down food and absorbs nutrients. Each of these groups plays a vital role in maintaining the body's function, but only the heart, blood, and blood vessels are components of the circulatory system.