Concept:An ammeter can measure potential difference by connecting a high resistance in series to limit current flow.Explanation:A voltmeter needs very high resistance so it draws only a tiny current from the circuit.This high series resistance is known as a multiplier.When a multiplier is connected in series with an ammeter (or galvanometer), the instrument measures voltage safely.The multiplier extends the range of the meter without altering the measured circuit significantly.Therefore, the correct device used for this adaptation is a multiplier, not a shunt or rheostat.Answer:B. multiplier