this one is easy..

we know that horizontal range $R = \frac{u^{2} \times \sin 2\theta}{g}...................(1)$ and height $H= \frac{u^{2} \times \sin^{2}\theta}{2g} .................(2)$ dividing $(2)$ by $(1)$ we get $\frac{H}{R}=\frac{\tan\theta}{4} =\frac{1}{4 \times \sqrt{3} }$ which gives $\tan\theta= \frac{1}{\sqrt{3}}= \tan 30^{o}$ hence $\theta=\boxed{30^{o}}$