Answer:
B. 720 kilocalories
Step-by-step explanation:
The primary consumers use about 90% of available energy pyramid for their physical functions. In order to solve this exercise, we need to calculate the 90% of 800 kilocalories.
We can state that there is a direct linear relationship between the kilocalories and the percentage. This means that for a higher percentage the amount of kilocalories will be greater.
We can write :

Where the denominators are percentages.
Solving for x :


The correct option is B. 720 kilocalories