Mark the correct alternative in each of the following:

Let  be angle of elevation of sun.

Given that: length of road  and its shadow 

Here, we have to find angle of elevation of sun.

So we use trigonometric ratios.

In a triangle,

$\Rightarrow \tan C=\frac{A B}{B C}$

$\Rightarrow \tan \theta=\frac{1}{\sqrt{3}}$  $\left[\because \tan 30^{\circ}=\frac{1}{\sqrt{3}}\right]$

$\Rightarrow \theta=30^{\circ}$

Hence the correct option is $a$.