(C)
Explanation:
The circle has a radius r = 0.5 m, which means that its circumference C is

One revolution means that the stopper travels a distance equal to the circumference of the circle so the velocity of the stopper is

Its to capture light or to focus. don't forget to like. :D
3 protons should be your answer
But we do not know whether the force is pushing or pulling (the same direction (both forces are parallel) but: .........[ ]<-F-- or .......[ ]--F-->). I suppose the correct answer is B