Correct option is (a) lyophilization
The best I can explain: Ultrasonication and homogenization are the physical methods used to extract enzymes from cells. Dialysis is a step involved in purification. Whereas lyophilization can be used to remove ethanol traces from protein precipitate. Another way is to keep the tubes in an inverted position in a deep freezer for a few minutes to allow extra ethanol to drain and then wipe off the extra traces by tissue paper.