Right answer is (a) Specific elution
For explanation I would say: In affinity chromatography, when the elution is done by creating a competition between the bounded enzymes with its suitable complementary protein in solution, the elution is referred to as specific elution. Nonspecific elution is done when specific ligand fail to elute desired enzyme. Filtration is separation method based on the size. Dialysis is a separation technique in which large molecules are retained in the membrane eluting the smaller molecules.