Which statements are true? choose all answers that are correct. a. all rectangles are parallelograms. b. all squares are rectangles. c. all squares are rhombuses. d. all rhombuses are trapezoids.

The correct answers are:
A, B and C.

Explanation:
A parallelogram is a quadrilateral with both pairs of opposite sides parallel.
A rectangle is a parallelogram with all right angles, so yes, every rectangle is a parallelogram.
A square is a parallelogram with all right angles and all congruent sides; since it is a parallelogram with all right angles, every square is a rectangle.
A rhombus is a parallelogram with all congruent sides.
Since a square is a parallelogram with all congruent sides, then every square is a rhombus.
A trapezoid is a quadrilateral with one pair of parallel sides. Since a rhombus is a parallelogram, with 2 pairs of parallel sides, rhombus are not trapezoids.