A classmate said that line AB and line DC are parallel based on the diagram below. Explain your classmates error.

Explanation:
The only information we have to go on is that ∠AWZ ≅ ∠XYC. However, these are not specific kinds of angles that can prove lines parallel. If we had a pair of alternate interior angles, such as ∠AWZ and ∠WZY, we could say that the lines are parallel. However, we do not have enough information.