Final answer:
A square is related to parallelograms, rhombuses, and rectangles in that it is a special type of rectangle with equal sides. Not all rectangles are squares, as only squares have all equal sides. A rectangle is always convex due to the nature of its interior angles being less than 180 degrees.
Step-by-step explanation:
The question asked relates to the properties of geometric shapes, specifically how a square relates to other quadrilaterals, including parallelograms, rhombuses, and rectangles, and why a rectangle is considered a convex quadrilateral. The statement 'C) All squares are rectangles, but not all rectangles are squares' is accurate because while both a square and a rectangle have four right angles, only a square has four sides of equal length, a defining characteristic that differentiates squares from rectangles. A rectangle is a convex quadrilateral because it is a four-sided shape with all interior angles less than 180 degrees, meaning it bulges outwards, which is the definition of convex.