Which one of the following shapes has only 1 line of symmetry?

1. Determine the number of lines of symmetry for each given shape

• A general parallelogram has $0$ lines of symmetry.
• A regular hexagon has $6$ lines of symmetry.
• A regular octagon has $8$ lines of symmetry.
• An isosceles trapezium has exactly $1$ line of symmetry (passing through the midpoints of the parallel sides).

2. Identify the correct option

The isosceles trapezium is the only shape with exactly $1$ line of symmetry.