问题
选择题
It's difficult ______ the old people ______ walk up the Great Wall. [ ]
A. for, for
B. to, to
C. for, to
D. to, for
答案
答案：C
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It's difficult ______ the old people ______ walk up the Great Wall. [ ]
A. for, for
B. to, to
C. for, to
D. to, for
答案：C