Hematology is primarily the study of which bodily fluid?

Hematology is primarily the study of blood and its components, including red blood cells, white blood cells, platelets, and plasma. This field focuses on understanding the causes, diagnosis, treatment, and prevention of blood-related disorders such as anemia, clotting disorders, and leukemia. Blood serves as a critical bodily fluid that transports oxygen, nutrients, and waste products throughout the body, making it a central focus of study in hematology.

The other options represent fluids or materials that are not the primary focus of hematology. Plasma is a component of blood rather than a separate entity studied independently. Urine pertains to nephrology and the study of the urinary system, while tissues relate more closely to pathology and histology, but do not encompass the study of blood, which is the essence of hematology.