Some ____________ are trapezoids, but others are not.

The correct answer is parallelograms.

Explanation: While all trapezoids are defined as quadrilaterals with at least one pair of parallel sides, some parallelograms, such as rectangles or rhombuses, do have that property and can be classified as trapezoids. However, parallelograms include shapes that are not trapezoids as well. Hence, it’s accurate to say some parallelograms are trapezoids, but not all trapezoids are parallelograms.