The correct option is B
OB: Radius; AC: Diameter; AD: Chord
The given figure of the path in which the horse moves is:
From the figure, we can observe that O is the centre of the circular path, and A, B, C, and D are the poles on the path.
After joining the points, we observe that
OB is the radius of the circle, O is the centre, and B is a point on the circumference of the circle.
AC is the line passing through the centre of the circle, and both its ends are on the circumference of the circle. It means that AC is the diameter of the circle.
AD is also a line whose ends are on the circumference of the circle, but it does not pass through the centre. This means that AD is a chord of the circle.
Hence OB, AC, and AD are the radius, diameter, and chord of the circular path respectively.