题干
—To be a promising student is not an easy job. It takes time.
—I can't agree more. ____________. There is no short cut.
A：All roads lead to Rome
B：Slow but sure wins the race
C：Practice makes perfect
D：Rome is not built in a day
答案(点此获取答案解析）
D
中，可以构成从集合
到集合
的映射的是（ ）
