A rhombus could also be called a rectangle because it has four sides and angles. If the rhombus is turned slightly it is a square; a rectangle could be classified as a square as long as it has four right angles and four sides. Whereas a square will be classified as a shape with four matching sides, two sets of parallel lines and four right angles. As long as the question doesn't ask about four congruent sides but has these other characteristics it is considered a rectangle.