A) Why are all parallelograms not rectangles?

b) Why are all rectangles not squares?

c) Why are all parallelograms not rhombi?

a) Rectangles always have 4 right angles (90 degrees), but parallelograms do not always have 4 right angles rather they can, but do not have to. Rectangles have to.

b) A square is a type of rectangle, but a rectangle is not a type of square. Both rectangles & squares have 4 right angles and are always quadrilaterals, but squares always have all sides that have the same length, but rectangles do not have to have their sides all equivalent lengths.

c) In the case of a parallelogram, the opposite sides are equal whereas in a rhombus all four sides are equal.