Answer: B
The two angles adjacent to side BC are in the ratio 4 : 5 ⇒ \( \frac{4}{9} : \frac{5}{9} \) \(\therefore\) The measures of the two angles = \(180^\circ \times \frac{4}{9},\ 180^\circ \times \frac{5}{9}\) = \(80^\circ,\ 100^\circ\)
The two angles adjacent to side BC are in the ratio 4 : 5 ⇒ \( \frac{4}{9} : \frac{5}{9} \) \(\therefore\) The measures of the two angles = \(180^\circ \times \frac{4}{9},\ 180^\circ \times \frac{5}{9}\) = \(80^\circ,\ 100^\circ\)