What is another (more descriptive) name for each polygon described below?  

1. A regular polygon with an exterior angle measuring $120°$.

   Answer (a):

   equilateral triangle

2. A quadrilateral with four equal angles.

   Answer (b):

   rectangle because all angles would be $90°$.

3. A polygon with an interior angle sum of $1260°$.

4. A quadrilateral with diagonals that are perpendicular bisectors of each other.