Geometry

Question Analysis：
This question tests the core property that diagonals in a parallelogram bisect each other, meaning their midpoints are the same point.
The main focus is recognizing that midpoints coincide in a parallelogram.

Key Concept Explanation:
In a parallelogram, the diagonals intersect at their midpoints.
Therefore, the midpoint of one diagonal is identical to the midpoint of the other diagonal.

Step-by-Step Solution：
Recall that in any parallelogram, diagonals bisect each other.
Thus, their midpoints are the same point, so the distance between them is 0 cm.

Option Analysis：
A) Correct: Midpoints coincide in a parallelogram.B/C/D) Incorrect: Misinterpret the question a...