A 2 volt battery, a `15 Omega` resistor and a potentiometer of `100 cm` length, all are connected in series. If the resistance resistance of potentiometer wire is `5 Omega`, then the potential gradient of the potentiometer wire is
A. `0.005 V//cm`
B. `0.05 V//cm`
C. `0.02 V//cm`
D. `0.2 V//cm`