If it was an heptagon it would have 14 diagonals
A circle.
There is only one line (or line segment) that can be drawn between two distince points.
One
Seven.
line segments
66 ( 12 nCr 2 )
Such polygon is called a heptagon.
11, I believe.
It is an imaginary line drawn through the same segments of the same limb in different animals, to indicate those segments which have the same relative position in each animal.
They can not be line segments on the same line, but they can both be line segments.
A square, a rectangle, a quadrilateral, or a trapezoid. (there's more, but I won't bore you)
twenty