8.many cities inthe southern part of the united states have difficulty ______traffic flowing when
问题描述：
8.many cities inthe southern part of the united states have difficulty ______traffic flowing when
8.many cities inthe southern part of the united states have difficulty ______ traffic flowing when it snows.
A)kept
B)to keep
C)keeping
D)in being kept
答
have difficulty in doing sth
have trouble in doing sth.
你可以把它看成是习惯搭配.这里不能用动词不定式.