**Core Concept**
Medullary thyroid carcinoma (MTC) is a type of thyroid cancer that originates from the C-cells of the thyroid gland. The C-cells produce calcitonin, a hormone involved in calcium homeostasis.

**Why the Correct Answer is Right**
MTC is a neuroendocrine tumor that arises from the parafollicular cells, also known as C-cells, of the thyroid gland. These cells are responsible for producing calcitonin, a hormone that helps regulate calcium levels in the blood. The diagnosis of MTC is often confirmed by elevated levels of calcitonin in the blood. The tumor can be sporadic or familial, with the latter often associated with multiple endocrine neoplasia type 2 (MEN2) syndrome.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it refers to papillary thyroid carcinoma, which arises from the follicular cells of the thyroid gland, not the C-cells.
**Option B:** This option is incorrect because it refers to anaplastic thyroid carcinoma, which is a highly aggressive and poorly differentiated form of thyroid cancer, but not specifically associated with the C-cells.
**Option C:** This option is incorrect because it refers to follicular thyroid carcinoma, which also arises from the follicular cells of the thyroid gland, not the C-cells.

**Clinical Pearl / High-Yield Fact**
MTC is often associated with elevated levels of calcitonin in the blood, which can be used as a tumor marker for diagnosis and monitoring of the disease.

**Correct Answer:** D. Medullary thyroid carcinoma (MTC)