Final answer:
Sunlight is the energy source for the light reactions; ATP produced from these light reactions serves as the energy source for the carbon reactions in the process of photosynthesis.
Step-by-step explanation:
The energy source for the light reactions is sunlight; the energy source for the carbon reactions is ATP. Therefore, the correct answer to the question is B. sunlight, ATP. During photosynthesis, the light-dependent reactions use energy from sunlight to produce ATP and NADPH. These are energy-carrying molecules that drive the light-independent reactions, also known as the Calvin Cycle. In these light-independent reactions, ATP provides the necessary energy while the absorbed carbon dioxide is fixed into sugars.
In summary, sunlight is captured by chlorophyll during the light reactions to generate ATP and NADPH. These molecules are then utilized in the Calvin Cycle, where carbon dioxide is ultimately transformed into organic molecules like glucose, using the chemical energy stored in ATP.