Consider the corresponding diagram,
The figure forms a right triangle with height 3 ft. and hypotenuse 5 ft.
The trigonometric function 'sine' relates the height, hypotenuse, and the angle. So it is better to use sine function here,
[tex]\sin \theta=\frac{3}{5}\Rightarrow\theta=\sin ^{-1}(\frac{3}{5})\approx36.9[/tex]Thus, the angle of elevation is 36.9 degrees approximately.
Therefore, option (b) is the correct choice.
