(d)
$We\ have\ ,\ y = x + \frac{4}{x^{2}}$
On differencing with respect to x, we get
$\frac{dy}{dx} = 1 - \frac{8}{x^{3}}$
Since, the tangent is parallel to $x - axis,$ therefore
$\frac{dy}{dx} = 0$
$\Rightarrow \ \ \ \ \ \ \ x^{3} = 8\ \ \ \ \Rightarrow x = 2\ and\ y = 3$