**Core Concept**
Teeth and cartilage are characteristic features of a rare ovarian tumor, which arises from the surface epithelium of the ovary and is known as a **teratoma**. Teratomas are a type of germ cell tumor that can contain tissues from all three germ layers: ectoderm, endoderm, and mesoderm.

**Why the Correct Answer is Right**
The correct answer is a type of ovarian teratoma, specifically a **dermoid cyst** (mature cystic teratoma). This tumor contains well-differentiated tissues, including teeth, cartilage, and sometimes even hair, muscle, and bone. The presence of teeth and cartilage is due to the abnormal development of the ectodermal and mesodermal tissues within the tumor. Dermoid cysts are often benign and can occur in young women, typically presenting as a pelvic mass.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a type of ovarian tumor that contains teeth and cartilage.
* **Option B:** This option is incorrect because it is a type of ovarian tumor that is primarily composed of malignant cells, not a teratoma.
* **Option D:** This option is incorrect because it is a type of ovarian tumor that is primarily composed of epithelial cells, not a teratoma.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a pelvic mass, it is essential to consider the possibility of a dermoid cyst, especially in young women. Dermoid cysts can be distinguished from other ovarian tumors by their characteristic radiographic features and the presence of well-differentiated tissues.

**Correct Answer: C. Dermoid cyst.**