I think it is C. 60.
You can eliminate A because it is not a right angle, and D because the angle is bigger than the given angle. So it is between 50 and 60, and I hope this is right and the picture makes sense
You can eliminate A because it is not a right angle, and D because the angle is bigger than the given angle. So it is between 50 and 60, and I hope this is right and the picture makes sense