Correct option is (d) Activity
To explain: Enzymes are sold on the basis of overall activity and hence it of prime importance to the enzyme producer and customer. Usually, the freshly prepared enzyme will have higher activity so that the enzyme preparation will have guaranteed storage life. The storage conditions and expected rate of loss of activity for a particular enzyme is given by the manufacturer. Hence it is important the customers follow the instruction by the manufacturer so that the enzyme activity may be retained during storage and use.