**Core Concept**
Ovarian tumors are a diverse group of neoplasms that arise from the ovarian tissue, which is composed of epithelial, stromal, and germ cell components. The majority of ovarian tumors are benign, but a significant proportion can be malignant, posing a serious health risk to affected women.

**Why the Correct Answer is Right**
The correct answer is **C. Surface epithelial cells**. Surface epithelial tumors, also known as epithelial ovarian cancers, are the most common type of ovarian cancer, accounting for about 90% of all cases. They arise from the surface epithelium of the ovary, which is a layer of cells that covers the surface of the ovary. These tumors are thought to arise from the transformation of normal surface epithelial cells into malignant cells, possibly due to genetic alterations or environmental factors.

**Why Each Wrong Option is Incorrect**
**Option A:** Germ cell tumors are a distinct category of ovarian tumors that arise from the germ cells, which are the cells responsible for producing eggs. While germ cell tumors can be malignant, they are much less common than surface epithelial tumors.
**Option B:** Stromal tumors arise from the stromal cells, which are the connective tissue cells that support the ovarian tissue. While stromal tumors can be malignant, they are relatively rare compared to surface epithelial tumors.
**Option D:** The correct answer is not listed, but it is likely that the other options are distractors.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the risk of developing ovarian cancer increases with age, and the majority of cases are diagnosed in postmenopausal women. Regular pelvic exams and transvaginal ultrasounds can help detect ovarian tumors early, improving treatment outcomes.

**Correct Answer: C. Surface epithelial cells**