The correct option is A water
When PS-II absorbs a photon, an electron in its P-680 reaction centre gets excited and escapes from it. To replace this electron, a water molecule is split into protons, electrons and oxygen molecule. This process of splitting of water is called photolysis. The resultant electron is taken up by the P-680 and becomes stable and ready to absorb the next photon. This process generates the molecular oxygen, which is an important byproduct of photosynthesis.