When two salamander species, the red-backed salamander and the valley-and-ridge salamander, occur without the other present, their jaw structures are identical, and they consume the same prey. However, when the two species co-occur, the red-backed salamander has a slower closing, stronger jaw, while the valley-and-ridge salamander has a faster closing, smaller jaw, and the two species consume different prey sizes. Which of the following is suggested by these observations? a. Competitive exclusion
b. Preemptive competition
c. A trade-off between growing fast and competing well
d. Character displacement