Which of the following is NOT a function of blood?

Blood serves several critical functions in the body, and understanding these can help clarify why certain options may not fit within the roles of blood.

Thermoregulation is a vital function of blood, as it helps to maintain the body's temperature by redistributing heat through circulation. This process is essential for ensuring that various tissues receive adequate warmth or cooling, depending on their needs.

Protection is another key role of blood. It carries immune cells that help defend against infections and foreign invaders, and it contains clotting factors that prevent excessive bleeding following an injury.

Transport is arguably one of the most fundamental roles of blood, as it is responsible for moving oxygen from the lungs to the body’s tissues and carbon dioxide from the tissues back to the lungs. It also carries nutrients, hormones, and waste products to and from cells, ensuring that the body functions efficiently.

In contrast, digestion involves the breakdown of food into nutrients and does not involve blood directly. While blood may transport the nutrients after digestion, the act of digestion itself occurs in the digestive system, not as a function of blood. Thus, this distinction confirms that digestion is not a function of blood, making it the correct answer to the question.