Answer:
Step-by-step explanation:
Ok the first box is the vertical angle theorem because AOD and COB and the other two are opposite angles formed by the same lines which means that they are vertical angles and the theorem proves that they are equal.
The next one is SAS because as you can see in the diagram, because we know the vertical angles are equal we now know that the triangles are congruent because there are two sides and an angle between them on both triangles that are equal.
The next one is CPCTC which stands for Corresponding Parts of Congruent Triangles Congruent this basically means that because the triangles are congruent, the sides that match up and angles that match up in the triangles are equal.
After that you would use Converse Alternate Interior Angle Theorem because in the previous step you already proved that the alternate interior angles in this structure are equal through congruent triangles and now you are saying that because the are equal the lines must be parallel because alt interior angles are only equal when lines are parallel. You have to use the converse because you are kind of going backward. If you used the regular one you would be using parallel lines to state that the angles are equal. Let me know if you have any questions and good luck!