**Correct option is: C) 12**

We have the height of the tree is BC = 12 m.

Angle of elevation of the sum is \(\angle\)A = \(45^\circ\)

In right \(\triangle\)ABC,

\(\frac {BC}{AB}\) = tan A = tan \(45^\circ\) = 1

= AB = BC = 12 m

Hence, the length of the shadow of the tree is 12 m.