# Which of the following is not a characteristic of all parallelograms?

a. Opposite sides are equal.

b. Adjacent angles are congruent.

A parallelogram is a quadrilateral having two pairs of parallel and equal sides.

## Answer: The characteristic which is not true for all parallelograms is adjacent angles are congruent.

Lets us understand the concept below.

**Explanation:**

In the figure, one can observe that adjacent angles of a parallelogram are acute and obtuse respectively.

∠A or ∠BAD and ∠C or ∠BCD are obtuse, ∠B or ∠ABC, and ∠D or ∠ADC are acute.