The correct option is
A remains constant for a cell
The cell constant, K, is equal to the distance in cm between the probe's electrodes divided by the surface area of the electrodes in cm2.
For solutions with low conductivities, the electrodes can be placed closer together or made larger so that the cell constant is less than one.
For a particular conductivity cell, the cell constant remains the same even if-
The electrolyte is changed.
The concentration of the electrolyte is changed.
The temperature of electrolyte is changed.
Hence, option B is correct.