We have the following statements and results.
A. A rhombus is a quadrilateral.
True. A rhombus is a quadrilateral all of which sides have the same length.
B. A quadrilateral is a polygon with four angles.
True. A polygon is a plane figure with at least three straight sides and angles, and typically five or more.
C. In quadrilateral PQRS, ∠P and ∠S are opposite angles.
False. If we have a quadrilateral PQRS, that means that ∠P and ∠S are consecutive angles, not opposite.
D. The diagonals of a rhombus are perpendicular and bisect each other.
True. It is true that the diagonals of a rhombus are always perpendicular and bisect each other.
Answer.
Statement C is false.