Answer: A
Between triangles \( \triangle AOB \) and \( \triangle COD \): - \( \angle OAB \) = alternate angle \( \angle ODC \) [because AB \( \parallel \) CD] - \( \angle OBA \) = alternate angle \( \angle OCD \) [because AB \( \parallel \) CD] - \( \angle AOB \) = vertically opposite angle \( \angle COD \) ∴ Triangles \( \triangle AOB \) and \( \triangle COD \) are similar. ∴ \( \frac{OA}{OD} = \frac{OB}{OC} \) ⇒ \( \frac{2}{4} = \frac{3}{OC} \) ⇒ \( OC = \frac{12}{2} = 6 \) ∴ \( OC = 6 \) cm.
Between triangles \( \triangle AOB \) and \( \triangle COD \): - \( \angle OAB \) = alternate angle \( \angle ODC \) [because AB \( \parallel \) CD] - \( \angle OBA \) = alternate angle \( \angle OCD \) [because AB \( \parallel \) CD] - \( \angle AOB \) = vertically opposite angle \( \angle COD \) ∴ Triangles \( \triangle AOB \) and \( \triangle COD \) are similar. ∴ \( \frac{OA}{OD} = \frac{OB}{OC} \) ⇒ \( \frac{2}{4} = \frac{3}{OC} \) ⇒ \( OC = \frac{12}{2} = 6 \) ∴ \( OC = 6 \) cm.