Which statement is true? a. all rectangles are quadrilaterals b. all quadrilaterals are rectangles c. all quadrilaterals are parallelograms. d. all quadrilaterals are squares.

The correct answer is:   [A]:  " All rectangles are quadrilaterals. "

Step-by-step explanation:

The other answer choices:

B, C, and D — are incorrect.

Not all "quadrilaterals" (which are "4-sides polygons") can be classified as {merely types of}: "rectangles" ;  or "parallelograms" ; or "squares".

It is true that All of the shapes — rectangles, parallelograms, and squares — which are mentioned in Answer choices:  [B], [C], and [D] , respectively — are, in fact,  types of quadrilaterals .

However, there are other types of quadrilaterals as well.  

For instance, all "rhombuses", or "rhombi",  and all "trapezoids" — as well as "kites" and 4 (four)-sided "arrowheads" are quadrilaterals, as well.

Furthermore, the choices provided within Answer choices:  [B]. {C] and [D]; are too limited in scope for other reasons, as well.  Read the following for more information and explanation.

Note that all "squares" are "rectangles", yet not all "rectangles" are "squares".  All "squares" are "rhombuses" (or, "rhombi"); as well as "parallelograms", yet not all "rhombuses" ["rhombi"] are squares — and not all parallelograms are squares.    

As such, all "rectangles" are "parallelograms", yet not all "parallelograms" are rectangles.

Note that all "rhombuses" {"rhombi"] are "parallelograms", yet not all "parallelograms" are "rhombuses" ["rhombi"].  

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the answer is 13 cm