**Core Concept**
Papillary carcinoma of the thyroid is a type of well-differentiated thyroid cancer characterized by its aggressive behavior and potential for lymph node metastasis. Tumor markers are substances produced by tumor cells that can be used for diagnosis, prognosis, and monitoring of cancer treatment.

**Why the Correct Answer is Right**
The tumor marker for papillary carcinoma of the thyroid is **Thyroglobulin (Tg)**. Thyroglobulin is a protein produced by thyroid cells, and its levels are often elevated in patients with papillary thyroid carcinoma. This is because thyroid cancer cells can continue to produce thyroglobulin even after the thyroid gland is removed. Elevated thyroglobulin levels can indicate recurrence or metastasis of the cancer.

**Why Each Wrong Option is Incorrect**
* **Option A:** Calcitonin is a tumor marker for medullary thyroid carcinoma, not papillary carcinoma.
* **Option B:** Carcinoembryonic antigen (CEA) is a tumor marker for various types of cancer, including colorectal, breast, and lung cancer, but it is not specific for papillary thyroid carcinoma.
* **Option D:** Tumor markers like alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) are associated with other types of cancer, such as hepatocellular carcinoma and choriocarcinoma, respectively.

**Clinical Pearl / High-Yield Fact**
It's essential to note that thyroglobulin levels can be elevated in patients with thyroiditis or other thyroid conditions, so a diagnosis of papillary thyroid carcinoma should be made in conjunction with clinical and radiological findings.

**Correct Answer:** C. Thyroglobulin