The height of a tower is $10 \;m$. Find the length of its shadow when sun's attitude makes an angle of $45^{\circ}$ to the horizontal

Question

$\begin{array}{1 1}(A) \; 20\;m \\(B)\; 10\;m \\(C)\;10 \sqrt 3\;m \\(D)\;\frac{10}{\sqrt 3}\;m \end{array}$