Consider the statement, every rectangle is a parallelogram.
Recall that a quadrilateral with both pairs of opposite sides parallel is called a parallelogram. Since this is true for every rectangle, it follows that every rectangle is a parallelogram.
Hence the statement is true.
Consider the statement, every parallelogram is a rectangle.
Notice that not all parallelograms are rectangles since for a rectangle, the interior angles must be right angles. This is not true for all parallelograms.
Hence the statement is false.
Consider the statement, every quadrilateral is a rhombus.
Recall that a parallelogram with four congruent sides is called a rhombus. Notice also that quadrilaterals are generally plane figures with four sides, so not all quadrilaterals are rhombuses.
Hence the statement is false.
Consider the statement, every rectangle with four congruent sides is a square.
Recall that a square is a parallelogram with four right angles and four congruent sides. Since a rectangle is a parallelogram with four right angles, it follows that when a rectangle has four congruent sides, it is a square.
Hence the statement is true.