Final answer:
Primary consumers receive about 10 percent of the energy from producers in an energy pyramid, so if there are 1,000 units at the producer level, primary consumers get 100 units. So the correct option is C.
Step-by-step explanation:
The question asks about the amount of energy passed from producers to primary consumers in an energy pyramid. Based on the ecological pyramid model, which shows only about 10 percent of the energy at one level is available to the next level, if producers have 1,000 units of energy, primary consumers would receive 100 units of that energy. The other 90 percent is used for metabolic processes or given off to the environment as heat. Therefore, the correct answer to the question is C. 100 units of energy.