1a) False. A square is never a trapezoid. A trapezoid has only one pair of parallel sides while the other set of opposite sides are not parallel. Contrast this with a square which has 2 pairs of parallel opposite sides.
1b) False. A rhombus is only a rectangle when the figure is also a square. A square is essentially a rhombus and a rectangle at the same time. If you had a Venn Diagram, then the circle region "rectangle" and the circle region "rhombus" overlap to form the region for "square". If the statement said "sometimes" instead of "always", then the statement would be true.
1c) False. Any rhombus is a parallelogram. This can be proven by dividing up the rhombus into triangles, and then proving the triangles to be congruent (using SSS), then you use CPCTC to show that the alternate interior angles are congruent. Finally, this would lead to the pairs of opposite sides being parallel through the converse of the alternate interior angle theorem. Changing the "never" to "always" will make the original statement to be true. Keep in mind that not all parallelograms are a rhombus.
