问题补充:
The law says that all public buildings must be accessible to people who have trouble .
A. walking
B. walk
C. to walk
D. walked
答案:
(答案→)A. walking
B. walk
C. to walk
D. walked
解析:考查固定句式。固定搭配have some trouble (in) doing sth做某事有困难;句意:法律规定,所有的公共建筑都要让那些步行有困难的人很容易就进入了。故A正确。