题干
It takes us ________ hour to go there by ________ bus.
A：an, a
B：a, an
C：an; /
D： a, /
答案(点此获取答案解析）
C
It takes us ________ hour to go there by ________ bus.
A：an, a
B：a, an
C：an; /
D： a, /
满足
，且
不是
的子集，则
