The fundamental problem （ ） their inability to distinguish betwe

The fundamental problem （ ） their inability to distinguish between reality and invention.
A、is proportionate to
B、is composed of
C、lies in
D、relies on
【正确答案】：C
【题目解析】：本题考查动词短语辨析。be proportionate to“成比例”， be composed of“由…构成”， lie in“在于”， rely on“依靠”。句意：最根本的问题在于他们无法分清现实和虚构。故选C。