When light is incident on a doubly refracting crystal,two refracted rays-ordinary ray ($O$-ray) and extraordinary ray ($E$-ray) are produced. Then:

• A
  Both $O$-ray and $E$-ray are polarised perpendicular to the plane of incidence.
• B
  Both $O$-ray and $E$-ray are polarised in the plane of incidence.
• C
  $E$-ray is polarised perpendicular to the plane of incidence and $O$-ray in the plane of incidence.
• D
  $E$-ray is polarised in the plane of incidence and $O$-ray perpendicular to the plane of incidence.