A line segment is symmetrical about

1. any line perpendicular to it.
2. any line passing through its mid-point
3. any line parallel to it.
4. its perpendicular bisector.

A scalene triangle has

1. no line of symmetry
2. one line of symmetry
3. two lines of symmetry
4. three lines of symmetry

A circle has

1. no line of symmetry
2. one line of symmetry
3. two lines of symmetry
4. an unlimited number of lines of symmetry

The line of symmetry of a rectangle are

1. its four sides
2. its two diagonals
3. the bisectors of its four interior angles
4. the lines joining the midpoints of its opposite sides.