Every cyclic parallelogram is a/an :

1. square

2. rhombus

3. rectangle

4. isosceles trapezium

Given,

ABCD is a cyclic parallelogram.

∠ABC = ∠ADC [Opposite angles of parallelogram are equal]

∠ABC + ∠ADC = 180° [Sum of opposite angles of cyclic quadrilateral is 180°]

∠ABC + ∠ABC = 180°

2∠ABC = 180°

∠ABC = $\dfrac{180^{\circ}}{2}$

∠ABC = ∠ADC = 90°

A parallelogram one of whose angle is 90° is a rectangle.

Hence, Every cyclic parallelogram is a rectangle.

Hence, option 3 is the correct option.