Which statement best describes a rhombus?

• A. All four sides are equal in length
• B. All angles are 90 degrees
• C. Diagonals are perpendicular and equal
• D. Opposite sides are not parallel

Answer: (A)

A rhombus is defined by having all four sides the same length. This equal-side property is what sets it apart, and it sits as a special kind of parallelogram, so opposite sides are parallel and opposite angles are equal. The diagonals of a rhombus cross at right angles, but they are not generally equal in length (they become equal only if the shape is a square). So, the statement that all four sides are equal most accurately describes a rhombus. The other descriptions either describe a square (right angles or equal diagonals) or contradict a basic feature of a rhombus (opposite sides not being parallel).