In this model, the producers in one area hold 10000 kcal of energy. Using the ten percent rule for transfer between trophic levels, about how much energy becomes available to the primary consumers?

Erklärung

The ten percent rule passes one tenth of 10000 kcal, which is 1000 kcal, to the next trophic level. The 9000 kcal choice is the amount that is lost rather than the amount transferred, so it answers the opposite question.