One of the first tests a physician might run to evaluate a patient's blood is:

A) CBC.
B) Hgb.
C) Rh factor.
D) transfusion.

CBC (Complete Blood Count) is one of the most common tests performed to evaluate a patient's blood. It provides information about the number and types of cells in the blood, including red blood cells, white blood cells, and platelets. This test can help diagnose and monitor a range of conditions, including anemia, infections, and leukemia. The other options listed are not typically the first tests run to evaluate a patient's blood. Hgb (hemoglobin) is a component of CBC and is not a separate test. Rh factor is typically only tested if someone is pregnant or if there is a history of a blood transfusion. Transfusion is not a test but rather a medical procedure.