The ray diagram could be correct 

• A

  $\text{ If }{\mathrm{n}}_1={\mathrm{n}}_2={\mathrm{n}}_{\mathrm{g}}$

• B

  $\text{ If }{\mathrm{n}}_1={\mathrm{n}}_2\text{ and }{\mathrm{n}}_1<{\mathrm{n}}_{\mathrm{g}}$

• C

  $\text{ If }{\mathrm{n}}_1={\mathrm{n}}_2\text{ and }{\mathrm{n}}_1>{\mathrm{n}}_{\mathrm{g}}$

• D

  Under no circumstances