Part A; What are all quadrilaterals with all sides that are congruent?
Rhombuses (including squares, which are usually considered special
cases of rhombuses)
Part B; What are all quadrilaterals with all sides that are congruent and have all congruent angles?
Squares
Part C; What are all quadrilaterals with only the opposite sides are congruent?
Parallelograms.
Edwin