$16.$ For a simple harmonic motion $($SHM$)$ the displacement x of the particle from the origin is given as a function of time by x$($t$)=$ xm cos$($t$+$$)$where the xm is the maximum displacement in units of meter, is the angular frequency in units of rad$/$s$,$ and is the phase constant. If the SHM is described as x$($t$)=0\mathrm{.}5$ cos $(20$ t $+$ $),$ the magnitude of the maximum acceleration is A$)10$ m$/$s$2$ B$)200$ m$/$s$2$ C$)100$ m$/$s$2$ D$)20$ m$/$s$2$