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A 2D Shape that has atleast one line of symmetry is a square. It has two.
[|] <- Example.
The 2D shape which has one line of symmetry is the trapezium.
A square
Square
An isosceles triangle and a kite have only one line of symmetry.
Septahedron
septahedron
a line
It doesn't have any volume (3D) and it's not a line (1D). Thus, it is a 2D shape.
2D shape
Regular polygon with any number of sides, circle, ellipse, isosceles triangle, rectangle, isosceles trapezium, kite, arrowhead.
1D a single line (?) 2D a flat shape 3D a cube
It's a 2D shape.