Potentiometry: 1)is the Measurement of the Electrical Potential Difference Between Two

Potentiometry:
1) is the measurement of the electrical potential difference between two electrodes
2) is measured in voltage
3) measurements require the use of reference electrodes
4) measurements are mode only when there is no flow of current

A) 1, 2, 3, 4
B) 1, 2, 3
C) 1, 2, 4
D) 2, 3, 4