A:x1•x2<0
B:x1•x3<0
C:x2•x3<0
D:x1+x2<0
20世纪60年代,在经济改革中试图摆脱苏联控制而遭苏联镇压的东欧国家是( )
— She has long hair, but my hair is much _________ than _________.