A rhombus has four equallength sides with opposite sides parallel to each other. The perimiter is the sum of the lengths of all sides (a + b + c + d) or, because all sides are the same length, 4 x length of one side (4s).
A(n) __________ is to a parallelogram as a square is to a rectangle.
rhombus 

trapezoid 

quadrilateral 

triangle 