Which combining form refers to blood?

The combining form that refers to blood is "hem/o." This term is derived from the Greek word "haima," meaning blood. It is commonly used in medical terminology to describe conditions, treatments, and components related to blood. For example, terms like "hemoglobin" (the protein in red blood cells that carries oxygen) and "hemorrhage" (excessive bleeding) incorporate the "hem/o" combining form to specify a connection to blood.

In contrast, "leuk/o" pertains to white blood cells or conditions related to them, such as leukemia. "Mamm/o" refers to breasts, primarily used when discussing mammography or conditions affecting breast tissue. "Nat/o" relates to birth or being born, often used in terms like "perinatal" or "neonatology." Thus, the correct answer focuses specifically on the term associated with blood, clearly distinguishing it from those linked to other biological aspects.