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
詳解 (共 1 筆)
未解鎖
此題考must 助動詞和頻率副詞的位置。...