Which of the following characteristics is true for all rhombuses?

A rhombus is defined as a quadrilateral with all four sides of equal length. One of its key characteristics is that opposite angles are equal. This means that if one pair of opposite angles measures, for instance, 60 degrees, the other pair will measure 120 degrees. This property holds true for all rhombuses regardless of their orientation or size.

By contrast, it's important to note that not all angles in a rhombus are 90 degrees; this characteristic would instead apply to squares, which are a specific type of rhombus. Additionally, the diagonals of a rhombus are not equal in length; they bisect each other at right angles but can differ in length. Lastly, since a rhombus has all sides of equal length, the idea that all sides are of different lengths is contradictory to the definition of a rhombus. Thus, the characteristic that all opposite angles are equal is a fundamental property of all rhombuses.