A Ball Attached to a String Moves in a Horizontal

Multiple Choice

A ball attached to a string moves in a horizontal circle of radius 1 m.It makes one revolution in 4 seconds.The magnitude of its acceleration is

A) 2.5 m/s².
B) 3.9 m/s².
C) 6.4 m/s².
D) 9.8 m/s².
E) 12.4 m/s².