Answer:
The answer of the question is 60° which is option(A).
here,
let one be suppose angle a°
a°+ 120° = 180° {being straight angle}or, a° = 180° - 120°
or, a° = 60°
a° = 60°
Now,
Let angle S be s°
s°+60°+60° = 180°{ the sum of angle of triangle is 180°}
or, s° = 180° - 120°
or, s° = 60°
therefore, angle S is 60°