Question

A particle is moving with a uniform speed in a circular orbit of radius r in a central force inversely proportional to the nth power of r. If the period of rotation of the particle is t, then:
(a) t ∝ r(n-2)
(b) t ∝ r(n-1)
(c) t ∝ rⁿ
(d) t ∝ r(n+1)