For this exercise it is important to remember what a "Quadrilateral is".
By definition, a Quadrilateral is 2-dimensional closed figure that has four straight sides.
A Rectangle is a Quadrilateral, because it has four straight sides and it is a flat shape.
Some of the properties of a Rectangle are the following:
1. All its interior angles measure 90 degrees (an angle that measures 90 degrees is also known as "Right angle").
2. Its opposite sides have equal length.
3. Its opposite sides are parallel.
4. Its diagonals bisect each other.
5. Its diagonals have the same length.
6. The sum of its interior angles is 360 degrees.
7. Its interior angles are congruent (they have equal measure).
8. It has four straight sides.
The answer is:
1. Its interior angles measure 90 degrees.
2. Its interior angles are congruent.
3. The sum of its interior angles is 360 degrees.
4. It has four straight sides.
5. Its opposite sides have equal length.
6. Its opposite sides are parallel.
7. Its diagonals bisect each other.
8. Its diagonals have the same length.