Correct answer is (b) Precipitation
Explanation: Precipitation is the step involved in purification of enzyme or protein. Gel filtration is a technique used to purify enzyme or protein. The steps involved are as follows:
(i) Gel preparation by using sponge like porous material which is equilibrated an applied in the column.
(ii) Sample application to the column which consists of different molecules.
(iii) To elute the sample, same solvent is applied to the column. Large molecules which cannot penetrate the gel, pass the column faster and get eluted first and smaller molecules they get penetrate the gel and take a longer time elute and thus, separating the sample of interest.