The oxygen evolved during photosynthesis, comes from water molecules. Which one of the following pairs of elements is involved in this reaction?

The oxygen evolved during photosynthesis, comes from water molecules. Manganese and chlorine are required for this reaction. The best known and most studied function of manganese is in photosynthetic oxygen evolution. In the form of a manganoprotein, manganese is part of the oxygen-evolving complex associated with photosystem II, where it accumulates charges during the oxidation of water.  Along with manganese, chloride is required for the oxygen-evolving reactions of photosynthesis