Answer the following question given this paragraph: 

Photosynthesis begins with the light reactions. It is during these reactions that the energy from sunlight is absorbed by the pigment chlorophyll in the thylakoid membranes of the chloroplast. The energy is then temporarily transferred to two molecules, ATP and NADPH, which are used in the second stage of photosynthesis. ATP and NADPH are generated by two electron transport chains . During the light reactions, water is used and oxygen is produced. These reactions can only occur during daylight as the process needs sunlight to begin.


Q: What is produced during the light reactions in photosynthesis?


A:
oxygen