The correct option is D Organic non–protein in nature and helps to activate metabolic enzymes
The cofactor is a non-protein part of the enzyme. It can be metal ions or the organic chemical. The cofactors which are organic chemicals are known as a coenzyme. These are loosely attached to the apoenzyme. The tightly bound coenzymes are the prosthetic group. It attaches with the apoenzyme and helps in enzyme activity.
So, the correct answer is option d.