From the figure , it is quite clear that the sides AB and AC have the same measure , i.e. , 8 units .
we know that ,
angles opposite to equal sides are equal.
therefore ,
∠B = ∠C = 30°
Now ,
angle sum property of a ∆ states that the sum of all the angles of a triangle equals 180°
thus ,
therefore ,
option ( c ) 120° is correct .
hope helpful ~