Question ID:PT69 S1 Q19 Passage:The goblin fern, which requires a thick layer of leaf litter on the forest floor, is disappearing from North American forests. In spots where it has recently vanished, the leaf litter is unusually thin and, unlike those places where this fern still thrives, is teeming with the European earthworm Lumbricus rubellus, which eats leaf litter. L. rubellus is thus probably responsible for the fern's disappearance. Stem:Which one of the following is an assumption on which the argument depends? Correct Answer Choice:EChoice A:Wherever there is a thick layer of leaf litter in North American forests, goblin ferns can be found. Choice B:None of the earthworms that are native to North America eat leaf litter. Choice C:Dead leaves from goblin ferns make up the greater part of the layer of leaf litter on the forest floors where the goblin fern has recently vanished. Choice D:There are no spots in the forests of North America where both goblin ferns and earthworms of the species L. rubellus can be found. Choice E:L. rubellus does not favor habitats where the leaf litter layer is considerably thinner than what is required by goblin ferns.