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 prey of different 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