Which Observation Led Ecologists to Conclude That Resource Limitation Is

Which observation led ecologists to conclude that resource limitation is not the only factor driving snowshoe hare cycles?

A) Some declining hare populations do not lack food.
B) Experimental addition of high quality food prevents hare populations from declining.
C) Hare reproductive rates peak several years before densities reach a maximum.
D) Hare population sizes rose and fell in synchrony across broad regions of the Canadian forest.