問題詳情
1. Unlike competitive runners, race walkers ____ some portion of their feet in contact with the ground.
(A) must to always keep
(B) must always keeping
(C) always must to keep
(D) must always keep
(E) always must keeping
參考答案
答案：D
難度：適中0.625
統計：A(0),B(1),C(1),D(5),E(0)