(d)
Given, $\frac{d}{dx}F(x) = \frac{e^{\sin x}}{x},\ x > 0$
On integrating both sides, we get
$F(x) = \int_{}^{}{\frac{e^{\sin x}}{x}dx}$ …(i)
Also $\int_{1}^{4}\frac{3}{x}e^{\sin x^{3}}dx = \int_{1}^{4}{\frac{3x^{2}}{x^{3}}.e^{\sin x^{3}}dx = F(k) - F(1)}$
Let $x^{3} = z \Rightarrow 3x^{2}dx = dz$
$\therefore\ \ \int_{1}^{64}\frac{e^{\sin z}}{z}dz = F(k) - F(1)$
$\Rightarrow \lbrack F{(z)\rbrack}_{1}^{64} = F(k) - F(1)$ [from Eq.(i)]
$\Rightarrow F(64) - F(1) = F(k) - F(1)$
$\Rightarrow k = 64$