一道英语选择题:有关数词形容名词
Toplantthetree,wemustdig________.
A.athreefeetdeephole
B.three-foot-deepahole
C.athree-feet-deephole
D.aholethreefeetdeep
A、B选项轻松排除,我选了C,但答案是D.
C项为什么不对呢