Which of the following is not a product of light reaction of photosynthesis?

The correct option is NADH. Light reaction is the first step of photosynthesis where solar energy gets converted into chemical energy. During this process, solar energy is absorbed by the chlorophyll and photolysis of water occurs. It releases hydrogen ion and oxygen. Hydrogen ion then compounds with NADP+ and forms NADPH (chemical form of energy). The light reaction also produces ATP by the chemiosmosis in the thylakoid membrane. Whereas, NADH is produced in respiratory cycles.