**Core Concept**
The ureter is a muscular tube that connects the kidney to the bladder, playing a crucial role in the urinary system. Identifying the ureter during surgical procedures is essential to avoid damaging it, which can lead to significant complications.

**Why the Correct Answer is Right**
The ureter is typically identified at operation by its characteristic color, known as the "ureteric sheen." This is due to the presence of a thin layer of adventitial tissue that contains blood vessels, giving the ureter a distinct pinkish hue. Additionally, the ureter is usually firmer and more rigid than surrounding tissues, making it easier to distinguish. The ureteric sheen is a result of the presence of a high concentration of smooth muscle cells in the ureteral wall.

**Why Each Wrong Option is Incorrect**
**Option A:** The ureter is not identified by its diameter, as it can vary in size depending on the individual and the location along its course.
**Option B:** The ureter is not identified by its location, as it can be difficult to locate, especially in complex surgical procedures.
**Option C:** The ureter is not identified by its attachment to the bladder, as it is a retroperitoneal structure and does not have a direct attachment to the bladder wall.

**Clinical Pearl / High-Yield Fact**
It is essential for surgeons to remember that the ureteric sheen is a reliable indicator of the ureter's location, and any deviation from this characteristic color should prompt further investigation to avoid ureteral injury.

**Correct Answer:** C.