**Core Concept**
Undescended testis, also known as cryptorchidism, is a condition where one or both testes fail to descend into the scrotum. The primary concern is the increased risk of testicular cancer, infertility, and testicular torsion. Early surgical intervention is crucial to prevent potential complications.

**Why the Correct Answer is Right**
Surgery for undescended testis is recommended at around 6-12 months of age. This timing is based on the principle that the testes continue to descend spontaneously in most cases until 9 months of age. If the testes have not descended by 12 months, it is likely that they will not descend on their own. Early surgical intervention, also known as orchiopexy, helps to bring the testes down into the scrotum, reducing the risk of complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because surgery is typically not recommended immediately at birth. Most pediatricians and urologists follow a "wait and see" approach for the first 6-12 months to allow for spontaneous descent.
* **Option B:** This option is incorrect because waiting until adolescence is too late. The risk of testicular cancer and other complications increases with age, making early intervention essential.
* **Option C:** This option is incorrect because there is no specific age range for surgery. While some surgeons may prefer to operate at a younger age, the general consensus is that 6-12 months is the optimal time for orchiopexy.

**Clinical Pearl / High-Yield Fact**
A mnemonic to remember the recommended age range for surgery is: "Six months, not six years, not six decades." This emphasizes the importance of early intervention to prevent potential complications.

**Correct Answer: C. 6-12 months of age.**