Which of the following is NOT a sub-component of red blood cells?

The correct answer identifies a component that is not classified as a sub-component of red blood cells. Neutrophils are a type of white blood cell, not a component of red blood cells. They play an essential role in the immune response by attacking pathogens and are part of the body's defense mechanism against infections.

In contrast, hematocrit refers to the proportion of blood volume that is occupied by red blood cells, making it directly related to the overall assessment of red blood cells. Reticulocytes are immature red blood cells and are part of the red blood cell development process, providing information about erythropoiesis, or the production of red blood cells. Mean Corpuscular Volume (MCV) measures the average size of red blood cells and is crucial in diagnosing various types of anemia and conditions related to red blood cell production.

Each of the other options directly pertains to the characteristics or statuses of red blood cells, while neutrophils do not fit into this specific category. This distinction is key for understanding the various components involved in hematology and the functioning of blood cells.