There is hardly an environment on earth some species of animals or other have not adapted

问题补充：

There is hardly an environment on earth some species of animals or other have not adapted successfully.

A. in which

B. on which

C. to which

D. for which

答案：

A. in which

B. on which

(答案→)C. to which

D. for which

解析：关系代词which代指先行词environment，介词to和动词adapt构成adapt to“适应”。

【标签】介词+关系代词