**Core Concept**
The development of the urogenital system in human embryos is a complex process involving the formation of the metanephros, ureteric bud, and cloaca. Abnormalities in this development can lead to various congenital anomalies, including double ureters.

**Why the Correct Answer is Right**
Double ureters are a type of congenital anomaly that occurs when there is a failure of the ureteric bud to properly differentiate and fuse with the metanephric mesenchyme. This can result in the formation of a second ureter that arises from a separate ureteric bud. The most likely embryonic structure to be involved in this process is the **ureteric bud**, which is responsible for the development of the ureters, renal pelvis, and calyces.

**Why Each Wrong Option is Incorrect**
**Option A:** The metanephros is responsible for the development of the renal parenchyma, including the nephrons and collecting ducts, but it is not directly involved in the formation of the ureters.

**Option B:** The cloaca is a structure that gives rise to the rectum, bladder, and urethra, but it is not directly involved in the formation of the ureters.

**Option C:** The mesonephros is a temporary kidney that is present during embryonic development, but it is not directly involved in the formation of the ureters.

**Clinical Pearl / High-Yield Fact**
A double ureter is a relatively rare congenital anomaly that can be associated with other urinary tract abnormalities, such as vesicoureteral reflux and obstructive uropathy. It is essential to perform a thorough imaging evaluation, including ultrasound and MRI, to diagnose and manage this condition.

**Correct Answer:** C.