Which is required for the light-dependent reactions in photosynthesis to occur?
h2o
atp
nadph
co2

The correct answer is- H2O ( water).

Photosynthesis is a process by which green plants and algae prepare their own food ( using CO2 and H2O) in the presence of sunlight. It is primarily divided into two phase that is light dependent and light independent phase.

During light depednent phase ( that occurs in thylakoid membrane), solar energy is absorbed by chlorophyll and converted into chemical energy in the form of ATP and NADPH.

Water is required as splitting of water ( H2O) occurs in this phase that liberates electrons ( which are passed to reaction center chlorophyll), hydrogen ions, and oxygen atom ( which combine to form oxygen molecule).

Thus, H2O is the right answer.