由0,1,2,这三个数字构成的三位数所组成的集合是( ) A:012,021,102,120,201,210 B:012,021,102,120,201,210
问题描述：
由0,1,2,这三个数字构成的三位数所组成的集合是( ) A:012,021,102,120,201,210 B:012,021,102,120,201,210
C:102,120,201,210 D:(±102,±120,±201,±210)
答
由0,1,2,这三个数字构成的三位数所组成的集合是(C )
A:012,021,102,120,201,210
B:012,021,102,120,201,210
C:102,120,201,210
D:(±102,±120,±201,±210)不懂??012,021数，前面不能为零:(±102,±120,±201,±210）前面加±号