A projectile fired from a gun has initial horizontal and vertical components of velocity equal to $30$ m$/$s and $40$ m$/$s$,$ respectively.

Reference: Ref $3-4$

What is the acceleration of the projectile when it reaches its maximum height?

A$.$

Its magnitude is $9\mathrm{.}8$ m$/$s$2$; and its direction is changing.

B$.$

zero m$/$s$2$

C$.$

$9\mathrm{.}8$ m$/$s$2,$ downward

D$.$

$4\mathrm{.}9$ m$/$s$2,$ downward

E$.$

less than $9\mathrm{.}8$ m$/$s$2$ and non$-$zero.