The source of hydrogen atoms for the synthesis of glucose is

Explanation

Water is the correct source of hydrogen atoms for glucose synthesis because, during photosynthesis, it is split in the light-dependent reactions to release hydrogen ions, electrons, and oxygen. The hydrogen ions and electrons are then used to reduce carbon dioxide into glucose in the Calvin cycle. NADH, FADH₂, and ATP are not sources of hydrogen in photosynthesis because they are mainly involved in cellular respiration, not in providing hydrogen for sugar formation. While ATP provides energy and NADPH supplies reducing power during photosynthesis, the actual hydrogen atoms come from water molecules.