辨一辨(在正确的说法后面打“√”,错误的说法后面打“×”) (1)a是平行线,b也是平行线......................( ) (2)a和b互相平行.....................................( ) (3)a和b都是平行线..................................( ) (4)a和b是一组平行线...............................( ) (5)a是b的平行线,b是a的平行线.............( ) (6)a的平行线是b,b的平行线是a................( )