The image of the pair of lines represented by ${\mathrm{ax}}^2+2\mathrm{hxy}+{\mathrm{by}}^2=0$ by the line mirror  y=0 is

• A

  ${\mathrm{ax}}^2-2\mathrm{hxy}-{\mathrm{by}}^2=0$

• B

  ${\mathrm{bx}}^2-2\mathrm{hxy}+{\mathrm{ay}}^2=0$

• C

  ${\mathrm{bx}}^2+2\mathrm{hxy}+{\mathrm{ay}}^2=0$

• D

  ${\mathrm{ax}}^2-2\mathrm{hxy}+{\mathrm{by}}^2=0$