d
Range $=\mathrm{R}=\frac{\mathrm{u}^{2}}{\mathrm{a}}=\frac{\mathrm{u}^{2} \mathrm{m}}{\mathrm{qE}}$ for $\theta=45^{\circ}$
$\mathrm{E}=\frac{\mathrm{u}^{2} \mathrm{m}}{\mathrm{qR}}$
$\frac{1}{2} \mathrm{mu}^{2}=\mathrm{KE}$
$\mathrm{E}=\frac{\mathrm{m}}{\mathrm{q} \mathrm{R}} \frac{2 \mathrm{KE}}{\mathrm{m}}=\frac{2(\mathrm{KE})}{\mathrm{qR}}$