A ray of light is incident at an angle of ${60}^{\mathrm{o}}$  on one face of a prism of angle ${30}^{\mathrm{o}}$ . The ray emerging out of the prism makes an angle of  ${30}^{\mathrm{o}}$ with the incident ray. The emergent ray is

• A

  Normal to the face through which it emerges

• B

  Inclined at  ${30}^{\mathrm{o}}$ to the face through which it emerges

• C

  Inclined at ${60}^{\mathrm{o}}$  to the face through which it emerges

• D

  None of the above