“元有天下,薄海内外,人迹所及,皆置驿传,使驿往来,如行国中。”这句话说明了( )
A:元朝中外交通的发达
B:元朝疆域的广大
C:元朝人口较少
D:元朝统一了中国
It ____ Mike nearly three hours ____ ____ his homework.