Correct Option: B

In photosynthesis, carbon dioxide is converted into sugars in a process called carbon fixation. Carbon fixation is a redox reaction, so photosynthesis needs to supply both a source of energy to drive this process, and the electrons needed to convert carbon dioxide into a carbohydrate, which is a reduction reaction. The general equation for photosynthesis is therefore: Carbon dioxide + electron donor + light energy → carbohydrate + oxidized electron donor.