To calculate the adjusted amount of energy that is available to organisms that are one trophic level above producers, you should consider the energy that is available after accounting for the energy used by producers for respiration.
The correct choice is:
D. Gross primary productivity minus amount of organic material used in respiration
This is because gross primary productivity (GPP) represents the total energy captured by producers through photosynthesis, while the amount of organic material used in respiration represents the energy that is lost as heat and used for metabolic processes. Therefore, the energy available to the next trophic level (which includes herbivores, or primary consumers) is the net primary productivity (NPP), which can be expressed as GPP minus the energy used in respiration.