OPTION 4

The option that is not a co-enzyme is Mn++ (Manganese ion).
Explanation:
🟥NAD (Nicotinamide adenine dinucleotide), NADP (Nicotinamide adenine dinucleotide phosphate), and FAD (Flavin adenine dinucleotide) are all co-enzymes that play essential roles in redox reactions, serving as electron carriers in various metabolic processes.
🟥Mn++ (Manganese ion), on the other hand, is a metal ion that serves as a cofactor, not a co-enzyme. It is often involved in enzyme catalysis by stabilizing charges or acting as a structural component of enzymes, but it does not serve the same electron-transfer role that co-enzymes typically perform.