The correct option is B Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1.
In colloidal, critical micelle concentration (CMC) is the concentration of surfactants above which micelles form and all additional surfactants added to the system go to micelles.
Below the CMC, the addition of surfactant to an aqueous solution causes an increase in the number of charge carriers and consequently, an increase in the conductivity. Above the CMC, further addition of surfactant increases the micelle concentration while the monomer concentration remains approximately constant (at the CMC level). Since a micelle is much larger than a SDS monomer it diffuses more slowly through solution and so is a less efficient charge carrier.