Final answer:
Voltage is the correct answer for what 110 volts measure in Rhonda's microcurrent device; it represents the electrical potential that drives current through a conductor.
Step-by-step explanation:
Rhonda's microcurrent device runs on 110 volts, which is a measure of the voltage through the conductor. Therefore, the correct answer is b) Voltage. Voltage is the electrical potential difference between two points and is the driving force that pushes electric current through a conductor. According to Ohm's law, the voltage (V) across a resistor equals the current (I) through the resistor times the resistance (R) of the resistor, which is mathematically represented as V = IR.