The chemical energy for the synthesis of sugar during the Calvin cycle is provided by the:

Explanation

The Calvin cycle, also known as the light-independent reactions or dark reactions of photosynthesis, relies on ATP for the energy to drive the synthesis of glucose. ATP is produced during the light-dependent reactions when light energy is converted into chemical energy. NADPH, another product of the light reactions, provides the reducing power, but ATP is crucial for the energy needs. Other molecules like FADH₂ and oxygen do not play a role in providing energy for this cycle. Therefore, ATPs generated by light reactions are the main source of energy for the Calvin cycle.