At least one otter species, the sea otter, has a large, often dominating, effect on the structure of its own habitat. There is no evidence that other species have ever exercised such (i)_____ effects. That lack of evidence could merely be because the other species have been studied less thoroughly. However, the size and density of the historic sea otter populations in many Pacific coastal regions (ii)_____ those of other otter species elsewhere, so perhaps the sea otter is indeed (iii)_____ in its effects on habitat.
答案：C,D,G