A Hartnell governor has its controlling force \(\mathrm{F}\) given by \(\mathrm{F}=\mathrm{p}+\mathrm{q}\), Where \(r\) is the radius of the balls and \(p\) and \(q\) are constants.

The governor becomes isochronous when

(a) \(p=0\) and \(q\) is positive

(b) \(p\) is positive and \(q=0\)

(c) \(p\) is negative and \(q\) is positive

(d) \(p\) is positive and \(q\) is also positive.