Final answer:
The copper sulfate method of determining the hemoglobin level is an indirect method.
Step-by-step explanation:
The copper sulfate method of determining the hemoglobin level is an indirect method. In this method, copper sulfate reacts with hemoglobin to form a color change, the intensity of which is proportional to the hemoglobin level in the blood sample. While this method is still used in some laboratories, it has been largely replaced by more accurate and reliable methods like the hemoglobin A1c test.