The correct option is D neither oxidation nor reduction at electrodes.
Salt bridge is a U–shaped inverted tube that contains a gel (paste of agar-agar powder) permeated with an inert electrolyte.
The criteria for an electrolyte to be used in salt bridge are :
1. The electrolytes should consist of cations and anions having same mobility.
2. The electrolytic ions should not react with the ions in the solution.
3. The electrolyte should not get oxidised/reduced at electrodes.