Answer:
(1) 120°
Explanation:
QOR is one-third of the the circle which angle at O is 120°.
Since the angles at Q and R have been bisected, then their angles are two times the bisected angle

Since two angles are 60° each, then triangle PQR is an equilateral triangle.
sum of interior opposite angles= exterior angle

Therefore the angle PRS is 120°
Also when you look at the angle closely, you would see the it is beyond right angle and all the other angles in the options which make 120° obviously the answer.