Researchers are studying optimal foraging distances for a bird population that feeds on fish living in nearby lakes. They have determined the net energy gained as a function of foraging distance for three different sizes of prey: small, medium, and large. The results are shown as markers in the graph below with their corresponding mathematical model fits shown as lines. Which of the following statements is consistent with the data in the figure and optimal foraging theory?
a. The birds will target medium prey because the birds are more likely to encounter them than large prey.
b. The birds will target medium prey because the net energy never goes below 0 and the optimal foraging distance is still smaller than for large prey.
c. The birds will target large prey because the net energy gained offsets the costs associated with larger foraging distance.
d. The birds will target small prey because the optimal foraging distance is smaller.