square, septagon (heptagon)!
A square dies because you can fold it across 😜.
A Line of Symmetry.
line of symmetry
A symmetrical shape. There are many different shapes that have one or more lines of symmetry and there is no other name associated with them as a group.
Line symmetry is another name for reflection symmetry. One half is a reflection of the other half. The line of symmetry is the line where you could fold the image and have both halves match exactly.
soda
Bisecting the line.
A square, hexagon
It is its diameter which gives a circle infinite lines of symmetry
You cannot have one parallel line. There must be another line that it is parallel to. Also, 1 symmetry is meaningless - you can have one axis of symmetry or rotational symmetry of order one. The answer will depend on which one it is.
Diameter