Geometry

Question Analysis:
This question involves the defining properties of a rhombus.
The main focus is on distinguishing rhombuses from other quadrilaterals like squares and rectangles.

Key Concept Explanation:
A rhombus is a parallelogram with all sides equal. Its key properties include:
Diagonals intersect at 90° and bisect each other.
Opposite angles are equal (but not necessarily 90°).
Diagonals are unequal unless it is a square.

Step-by-Step Solution:
Option A: Incorrect. Only squares (a type of rhombus) have 90° angles.
Option B: Incorrect. Rectangles have equal diagonals, but rhombuses do not.
Option C: Correct. Perpendicular diagonals are a defining feature of rhombuses.
Option D: Incorrect. All parallelograms, i...