The correct option is B Western blot
The confirmatory HIV test employs a western blot to detect anti-HIV antibody in a human serum sample. Proteins from unknown HIV-infected cells are separated and blotted on a membrane. Then, serum to be tested is applied, the free antibody has washed away and a secondary anti-human antibody linked to an enzyme signal is added. The stained bands then indicate the proteins to which the patient' serum contains antibody.
Thus, the correct answer is option B.