B is the right answer because you can set up a ratio like this:
[tex]tan(A) = (\frac{16.3}{16.3})[/tex]
If you solve for A, then you get:
[tex]A = tan^-1(\frac{16.3}{16.3})[/tex]
Hopefully this makes sense. Also, in the textbox, ∠A = 45° and your answer's B.
