The correct option is D coenzyme
Holoenzyme is made up of two parts. It consists of a protein part called apoenzyme and a non-protein part called the cofactor.
There are three kinds of cofactors - prosthetic groups, coenzymes and metal ions.
The organic cofactor includes the prosthetic group and coenzymes while metal ions form the inorganic part.
A coenzyme is an organic substance that binds with the apoenzyme and is essential for the action of an enzyme.
Enzymes whose amino acid sequence or structure varies but they catalyse the same reaction are called isoenzymes.