**Core Concept**
The patient's presentation of primary infertility and a palpable pelvic mass, along with an elevated CA-125 level, suggests a possible diagnosis of ovarian cancer. CA-125 is a tumor marker commonly elevated in epithelial ovarian cancer, but it can also be elevated in other conditions such as endometriosis, pelvic inflammatory disease, and benign ovarian tumors.

**Why the Correct Answer is Right**
The patient's symptoms of primary infertility and a palpable pelvic mass are classic presentations of ovarian cancer. The elevated CA-125 level supports this diagnosis, as it is a marker that is often elevated in epithelial ovarian cancer. The tumor marker CA-125 is produced by the epithelial cells that line the ovary, and its levels can be elevated in ovarian cancer due to tumor cell shedding into the peritoneal fluid.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not take into account the patient's elevated CA-125 level and the palpable pelvic mass, which are key diagnostic features of ovarian cancer.
**Option B:** This option is incorrect because it is too broad and does not specifically address the patient's symptoms and laboratory findings.
**Option C:** This option is incorrect because it does not consider the patient's age and the fact that ovarian cancer is more common in postmenopausal women.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that an elevated CA-125 level can be seen in various conditions, including ovarian cancer, endometriosis, and benign ovarian tumors. Therefore, a diagnosis of ovarian cancer should be made based on a combination of clinical symptoms, laboratory findings, and imaging studies.

**Correct Answer:** C. Ovarian cancer