A line has 180 degrees rotational symmetry.
Line symmetry.
Line symmetry = Reflection symmetry. Point symmetry = Rotational symmetry.
Yes
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.
Yes. Any equilateral shape can have both rotational and line symmetry.
A semicircle.
circle
A line segment would have rotational symmetry.
Yes, it is possible to have a shape that has a line of symmetry but does not have rotational symmetry. An example is the letter "K", which has a vertical line of symmetry but cannot be rotated to match its original orientation.
How about an isosceles trapezoid
The letters S, N, Z, for example.
A triangle........I think
Parrallelogram (it has rotational symmetry but no lines of symmetry)
The letters H and Z have both line symmetry and rotational symmetry
It has line symmetry (straight down the center) but not rotational symmetry.
A line has rotational symmetry of order 2.