In the diagram a || b. Use the diagram to answer the question. (Diagram not to scale.) Name the alternate interior angle to 7. A. 1 B. 2 C. 6 D. 4

Answer: B. 2
In the above diagram a || b. The alternate interior angle to 7 is 2. Alternate Interior Angles are a pair of angles which are situated on the inner side of each of two lines which are crossed by another line (called the transversal), but on opposite sides of the transversal.   In the given diagram, lines a and b are crossed by a transversal. Although 4 (Option D) is situated on the inner side of line a, it is on the same side of the transversal with 7 and therefore, is a conservative interior angle to 7. Conversely 2 (Option B) is also situated on the inner side of line a, 2 and 7 are on opposite sides of the transversal. Therefore, 2 and 7 are alternate interior angles.
Mathematically, alternate interior angles are equal, while the sum of two conservative interior angles is 180 degrees.