Question

Which of the following cannot be a cyclic quadrilateral?

• A. Square
• B. Rectangle
• C. Parallelogram
• D. Trapezium

Answer 1

The correct option is C

Parallelogram

A quadrilateral is cyclic if its opposite angles are supplementary.

In square, rectangle and isosceles trapezium, the opposite angles are supplementary, that is, the sum of the opposite angles is ${180}^{\circ }$.

In a parallelogram, the opposite angles are equal and may not add to ${180}^{\circ }$. Hence, a parallelogram cannot be a cyclic quadrilateral.