If \(|cos x|^{sin^2x -\frac32sinx+ \frac12} = 1\) , then possible values of x are
a. \(n\pi \;or\;n\pi + (-1)^n \frac \pi6, n\in I\)
b. \(n\pi \;or\;2n\pi + \frac \pi2\; or\;n\pi+ (-1)^n \frac \pi6, n\in I\)
c. \(\;n\pi + (-1)^n \frac \pi6, n\in I\)
d. \(n\pi, n\in I\)