When an electrical circuit is working properly , electrical current runs through that circuit.
Much of the circuit is in fact a comparator made with discrete transistors.
When a comparator made with discrete transistors is working properly , electrical current runs through it.
What has electrical current running through it when working properly?

a: a hydraulic system
b: Marathon runners.
c: deoxyribonucleic acid
d: The bending of a ray of light
e: Electrical tape.
f: Discrete transistors.
g: Ocean currents.
h: electromagnetic energy