Which of the following statements is not always true? a. in a rhombus, the diagonals bisect opposite angles. b. in a rhombus, the diagonals are perpendicular. c. in a rhombus, the diagonals are congruent. d. in a rhombus, all four sides are congruent. select the best answer from the choices provided a b c d

C. In a rhombus, the diagonals are congruent

Explanation:
A rhombus is a quadrilateral which has the following properties:
1- all sides are equal
2- diagonals are not equal, however, they bisect each other at 90°
3- opposite sides are parallel
4- diagonals bisect the angles
5- opposite angles are equal but not right

Now, a special type of rhombus is a square. The difference between the two is that:
1- all angles of a square are right angles
2- diagonals are equal and bisect each other at 45°

Based on the above, we can note that if diagonals of a rhombus became congruent, it would turn into a square (special type of rhombus).
This means that this condition is not essential for a quadrilateral to be a rhombus.

Hope this helps :)