**Core Concept**
Rhabdomyosarcoma is a type of soft tissue sarcoma that arises from skeletal muscle cells. The prognosis of rhabdomyosarcoma is influenced by various factors, including the site of the tumour, age of the patient, and tumour histology. In general, rhabdomyosarcoma is more aggressive and has a poorer prognosis when it occurs in certain sites.

**Why the Correct Answer is Right**
Rhabdomyosarcoma that occurs in the extremities (such as the limbs) tends to have a poorer prognosis due to its higher likelihood of metastasis and local recurrence. This is because tumours in the extremities are often larger and more aggressive at the time of diagnosis, making them more challenging to treat. In contrast, rhabdomyosarcoma that occurs in the head and neck region, such as in the orbit, tends to have a better prognosis due to its lower rate of metastasis and local recurrence.

**Why Each Wrong Option is Incorrect**
**Option A:** The orbit is actually one of the more favourable sites for rhabdomyosarcoma, with a higher rate of cure and lower rate of metastasis compared to tumours in the extremities.

**Option B:** Para-testicular rhabdomyosarcoma, which occurs near the testicles, has a relatively good prognosis due to its early detection and effective treatment options.

**Option D:** Rhabdomyosarcoma of the urinary bladder, although rare, tends to have a better prognosis compared to tumours in the extremities due to its relatively lower rate of metastasis and local recurrence.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the prognosis of rhabdomyosarcoma is highly dependent on the site of the tumour, with certain sites (such as the extremities) being associated with a poorer prognosis. This highlights the importance of accurate staging and histological classification in determining the optimal treatment plan for patients with rhabdomyosarcoma.

**✓ Correct Answer: C. Extremity**