What are the primary functions of blood?

The primary functions of blood are indeed to transport oxygen, nutrients, hormones, and waste products throughout the body. Blood serves as a vital fluid that carries oxygen from the lungs to the tissues and organs, while also returning carbon dioxide back to the lungs for exhalation. In addition to oxygen transport, blood delivers essential nutrients, such as glucose and amino acids, from the digestive system to cells that require them for energy and growth. Hormones produced by endocrine glands travel through the bloodstream to reach their target organs, facilitating various physiological processes. Furthermore, blood plays a crucial role in removing waste products, such as urea and creatinine, from the cells to excrete them through the kidneys, maintaining overall metabolic homeostasis.

While other choices mention important roles of blood or related systems, the primary focus of blood's main functions centers on transporting critical substances throughout the body, which is why this choice is deemed the most comprehensive and accurate.