Consider a thin prism.
Find the deviation (in degrees)
We will use the formula of deviation for thin prism.
!!delta = A(mu-1)!!, where !!A!! is prism angle and !!mu!! is refractive index of the prism.
!!delta = 2^0 (1.5-1)= 1^0 !!
Then it will reflect by mirror, so final deviation will be
!!=> 180^0 -1 = 179^0!!
Therefore option (c) is correct.