Research Summary. A simple experimental-layout diagram for microbial fuel cells states: Groups A and B use glucose; C and D use acetate. B and D use a carbon-cloth electrode. A complex results table reports peak voltage and current density: A: peak voltage 0.32, current density 42; B: peak voltage 0.51, current density 68; C: peak voltage 0.28, current density 35; D: peak voltage 0.46, current density 60. Which conclusion is supported when the layout and results table are combined?