Find the equations of the bisectors of the angle between the co-ordinate axes?

$(a)\;y=\pm x\qquad(b)\;y=\pm 2x\qquad(c)\;y=\pm 3x\qquad(d)\;y=\pm 4x$

Equation of bisector will be $y=mx$
$m=\tan 45^{\large\circ}=1$
Or $m=\tan 135^{\large\circ}=-1$
Hence equation of bisectors will be
$y=\pm x$
(i.e) $y=x$ &$y=-x$
Hence (a) is the correct answer.