Geometry

Question Analysis：
This question tests the ability to differentiate between the diagonal properties of general parallelograms and their special cases.
The main focus is recognizing that only general parallelograms have bisecting diagonals without additional constraints.

Key Concept Explanation:
Parallelogram: Diagonals bisect each other (no requirement for congruence or perpendicularity).
Rectangle: Diagonals bisect each other and are congruent.
Rhombus: Diagonals bisect each other and are perpendicular.
Square: Diagonals bisect each other, are congruent, and perpendicular.

Step-by-Step Solution：
Eliminate options:
A) Incorrect (diagonals are congruent).
B) Incorrect (diagonals are perpendicular).
C) Incorrect (diagonals have all properties)....