Which of the following would be expected to have the greatest impact on primary productivity? a. chemical energy b. nutrient availability c. solar energy d. water availability

The correct answer is option C. solar energy.

The primary productivity is the energy, which converted in organic material from the solar or the chemical energy. In the primary productivity, the energy obtained from the photosynthesis is the main source of energy. In case, the solar energy obtained varies, then the primary productivity would be directly affected.  

i believe the correct answer is d