During a wave motion in a medium particle is executing two different S$.$H$.$M$,$ mutually perpendicular, of different amplitudes and have phase difference of $\backslash (\backslash$pi $/2\backslash ).$ The path of the particle will be$.$

a$)$circular$.$

b$)$straight line.

c$)$ parabola.

d$)$elliptical