The decline of the mountain yellow-legged frog in the high reaches of the Sierra Nevada has become severe enough for the United States Fish and Wildlife Service quite possibly to list it as an endangered species in the near future.

(A) severe enough for the United States Fish and Wildlife Service quite possibly to list it
(B) severe enough so that the United States Fish and Wildlife Service could well list them
(C) severe enough for it quite possibly to be listed by the United States Fish and Wildlife Service
(D) so severe that the United States Fish and Wildlife Service could well list it
(E) so severe that they could well be listed by the United States Fish and Wildlife Service

OA D

Source: GMAT Prep