My Favourite Sport
My favourite sport is football. After school, I often play football with my friends. I work hard at school and I am on the football team. Sometimes I watch a football game at the gym. Pele is my favourite football player
关于北魏孝文帝改革的影响，下列说法中正确的是（ ）
现有四种说法：①－a表示负数； ②若|x|=-x，则x<0； ③绝对值最小的有理数是0；④3×102x2y是5次单项式；其中正确的是( )
编号
长度/cm
直径/cm
频率/Hz
1
20
1.5
2131
2
30
2.0
1284
3
50
2.5
656
