Tinbergen Observed That After Gull Nestlings Hatch, the Parents Remove

Tinbergen observed that after gull nestlings hatch, the parents remove the eggshells from the nest. To understand why (ultimate causation) , he painted chicken eggs to resemble gull eggs, which had camouflage coloration to allow them to be inconspicuous against the natural background. He distributed them throughout the area in which the gulls were nesting, placing broken eggshells with their prominent white interiors next to some of the eggs. As a control, he left other camouflaged eggs alone without eggshells. He then noted which eggs were found more easily by crows. Because the crows could use the white interior of a broken eggshell as a cue, they ate more of the camouflaged eggs that were near eggshells. Tinbergen concluded that eggshell removal behavior is adaptive: it reduces predation and thus increases the offspring's chances of survival.
-Rank these experiments from worst to best to study why gulls remove broken eggshells from their nests.

A) Place broken eggshells near white chicken eggs, and record predation by undergraduate students acting as "predators".
B) Place broken eggshells near real gull eggs, and record predation by crows.
C) Place broken eggshells near brown chicken eggs, and record predation by undergraduate students acting as "predators".
D) Place broken eggshells near brown chicken eggs painted with dark brown spots, and record predation by crows.
E) Place broken eggshells near brown chicken eggs painted with dark brown spots, and record predation by undergraduate students acting as "predators".