Geometry

Question Analysis:
This question involves deductive reasoning about the properties of quadrilaterals.
The main focus is on identifying a quadrilateral based on its side lengths and angles.

Key Concept Explanation:
A square has all sides equal and all angles equal to 90°.
A rhombus has all sides equal but angles are not necessarily 90°.
A rectangle has opposite sides equal and all angles equal to 90°.
A trapezoid has only one pair of parallel sides.

Step-by-Step Solution:
The quadrilateral has all sides equal, so it could be a square or rhombus.
One angle is 90°, so it cannot be a rhombus (which has no right angles unless it is a square).
Therefore, the quadrilateral must be a square.

Option Analysis:
A) Correct: The quadrilateral meets the definition of a square.