Concept:When two parallel lines are crossed by a transversal, alternate interior angles are equal. The sum of the three angles in any triangle is 180°.
Explanation:In the figure, AB ∥ DC and AC is a transversal.
So, alternate interior angle ∠CDO equals ∠ABO, which is 65°.
In triangle COD, ∠COD = 70° (given in figure).
Using angle sum property: ∠COD + ∠ODC + ∠OCD = 180°.
Substitute: 70° + 65° + ∠OCD = 180°.
Thus, ∠OCD = 180° – 135° = 45°.
Answer:45° (Option A)
