Answer:
B: All of the choices!
Explanation:
Choice 1: Simply, there is no current without voltage, so it DOES cause current.
Choice 3: Voltage DOES push free electrons around a circuit. Without it, free electrons will move around between atoms, but randomly, so they wouldn't be much use.
Choice 4: Voltage IS measured in volts, so this option is true as well.
Choice 2: Voltage is all of those answers, so it is true! :D
Hope i helped! :]
