The source of hydrogen atom for the synthesis of glucose is

Explanation

In the light-dependent reactions of photosynthesis, water (H2O) is split in a process known as photolysis. This process releases electrons, protons (hydrogen ions), and oxygen. The protons are used in the Calvin cycle to help reduce carbon dioxide into glucose. Therefore, water is the source of hydrogen atoms for glucose synthesis. NADP acts as an electron carrier, becoming NADPH after accepting electrons and protons but is not the initial source of hydrogen. FADH2 is not involved in photosynthesis, and ATP provides energy rather than hydrogen.