Many people claim that they have seen UFO with their own eyes I personally doubt.A. that

问题补充：

Many people claim that they have seen UFO with their own eyes, I personally doubt.

A. that

B. which

C. when

D. where

答案：

A. that

(答案→)B. which

C. when

D. where

解析：定语从句考查题。先行词为整个主句所以关系词只能用which而且关系词在从句中作宾语。句意：许多人声称他们看到了UFO我对此表示怀疑。