Final answer:
The correct statement about rhombuses is that their diagonals are perpendicular; this is a defining property of rhombuses as they intersect each other at right angles.
Step-by-step explanation:
The question is asking to identify a property that is always true for rhombuses. The correct statement regarding the diagonals of a rhombus is that they are perpendicular (option A). A rhombus is a type of parallelogram with all four sides of equal length. In a rhombus, the diagonals intersect each other at right angles (forming a 90° angle), and they bisect each other, but they are not congruent. Therefore, option B (The diagonals are congruent.) is incorrect, as is option C (The diagonals are not congruent and not perpendicular.) and option D (The diagonals are congruent and perpendicular.). Using the Pythagorean theorem, the relationship between the sides and diagonals of a rhombus when addressing their lengths can be explored further in mathematical problems involving geometry and vector addition.