severe enough和so severe that有什么区别

题目

severe enough和so severe that有什么区别
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 so severe that the United States Fish and Wildlife Service could well list it

答案

severe enough是“足够严重”,是副词enough修饰形容词的短语
和so severe that是“如此严重以至于.”,后接状语从句.