Assertion : For measuring resistance of an ionic solution an AC source is used.

Reason : Concentration of ionic solution will change if

DC source is used.

(i) Both assertion and reason are true and the reason is the correct explanation of assertion.

For measuring resistance of an ionic solution an AC (Alternating current) source is used because concentration of ionic solution will change if DC (Direct current) source is used. DC current can change the composition of the ionic solution.