What are the four main components of blood?

The four main components of blood are red blood cells, white blood cells, platelets, and plasma.

Red blood cells are responsible for transporting oxygen from the lungs to the tissues and returning carbon dioxide from the tissues back to the lungs, playing a crucial role in respiration. White blood cells are part of the immune system and are essential for defending the body against infections by identifying and destroying pathogens. Platelets are involved in the clotting process, helping to prevent excessive bleeding when injuries occur. Finally, plasma is the liquid component of blood that carries cells, nutrients, hormones, waste products, and proteins throughout the body.

The other choices include components that are either part of a subset of blood's functions or not components of blood at all. For example, hormones and glucose are substances that may be found in plasma but do not categorize the main components of blood itself. Similarly, amino acids and proteins are part of the body's biochemistry but are not classified as components of blood. Thus, the correct answer encompasses all four primary components that define blood's structure and function in the body.