Two.
A line has two fold rotational symetry.
yes
A Parallelogram, a Diamond and a rhombus all have rotational symetry of two. Others Kite 1 Trapezium 1 Square 4
None.
None.
A parallelogram has a rotational symmetry of 2!
circle
A general parallelogram has rotational symmetry of order two.
No.
Inifity ... symmetry ... parallelogram ... infinity ...
An equilateral triangle