The correct statement about the diameter of a sphere is:
The diameter of a sphere passes through the center of the circle.
To clarify the other statements:
- The diameter is a chord, specifically the longest chord possible in a sphere.
- The diameter is not the shortest length; rather, it is the longest distance across the sphere.
- The diameter is not 2.5 times the length of the radius; it is exactly 2 times the radius.
So, the fourth statement is the only true one.