隋朝时,一位商人从今天的杭州由水路到洛阳做生意,他先后要经过( )
A:永济渠、江南河、邗沟
B:通济渠、会通河、江南河
C:江南河、邗沟、通济渠
D:通惠河、江南河、邗沟
已知a>b,ab=2且a2+b2=5,则a﹣b=____
(2015.•广东佛山)I don't understand why more girls ________ to do housework than boys in today's society.