The diagonals of a rhombus are? a. perpendicular b. sometimes equal c. parallel d. never congruent

By definition we have that the diamond is:
 The rhombus is a parallelogram (and therefore a quadrilateral) whose four sides are of equal length and whose diagonals are cut perpendicularly.
 Therefore, its diagonals are perpendicular.
 
 The diagonals of a rhombus are:
 A. Perpendicular

I’m vary good with science if you need with that