A:22
B:2
C:1
D:2
若实数x、y、z满足(x-z)2-4(x-y)(y-z)=0,则下列式子一定成立的是( )
细胞内能储存遗传信息并能复制的物质是( )
一 I have made great progress in spoken English since last year.
一 Well done! I am sure you'll be good at it soon.