If ∠SMO measures 45°, what is the measure of ∠SMN ?A 180B 90C 45D 135

Given:
[tex]\angle SMO=45^{\circ}[/tex][tex]\begin{gathered} \angle SMO+\angle SMN=180^{\circ} \\ 45^{\circ}+\angle SMN=180^{\circ} \\ \angle SMN=180^{\circ}-45^{\circ} \\ \angle SMN=135^{\circ} \end{gathered}[/tex]