Correct choice is (c) Potentiometric biosensor
The best I can explain: In the above diagram, simplest form amperometric biosensor is shown. In amperometric biosensor, an electric potential is applied between the central platinum cathode and the annular silver anode in the presence of saturated solution of KCl which generates a current. This electrode compartment is separated from the Glucose oxidase (biocatalyst) by a thin plastic membrane that is permeable only to oxygen. The analyte solution is separated from the biocatalyst by another membrane which is permeable to the substrate and product.