Which quadrilateral has only a single line of symmetry?0.7xen-US1Rectangle2Square3Parallelogram4Isosceles trapezoid

The quadrilateral that has only a single line of symmetry is the Isosceles trapezoid.

Here's why:

1. Rectangle: A rectangle has two lines of symmetry - one that cuts it horizontally into two equal halves, and another that cuts it vertically into two equal halves.

2. Square: A square has four lines of symmetry - two that cut it diagonally into two equal halves, and two more that cut it horizontally and vertically into two equal halves.

3. Parallelogram: A parallelogram (that is not a rectangle or square) has no lines of symmetry. No matter how you try to cut it, you can't divide it into two mirror-image halves.

4. Isosceles trapezoid: An isosceles trapezoid has one line of symmetry - a vertical line that cuts it into two equal halves. The two non-parallel sides are of equal length, and the base angles are equal, making the two halves mirror images of each other.