10.若直线l1:x+ay−2=0l_{1}:x+ay-2=0l1:x+ay−2=0与l2:2x+(a2+1)y−2=0l_2:2x+(a^2+1)y-2=0l2:2x+(a2+1)y−2=0平行,则两直线之间的距离为((( )))