Which one provides electrons for reduction reactions in photosynthesis

Which one is directly involved in light reaction of photosynthesis

Indicate whether water undergoes oxidation or reduction during photosynthesis. Give the reaction involved.

Which one of these reactions occurs during photosynthesis

Oxidation reaction involves loss of electrons, and reduction reaction involves gain of electrons. The reaction in which a species disproportinates into two oxidation states ( lower and higher) is called disproportionation reaction. Which of the following is not a dispropotional reaction?