**Core Concept**
Meig's syndrome is a clinical entity characterized by the presence of an ovarian tumor, ascites, and pleural effusion, which resolve after removal of the tumor. The syndrome is often associated with a specific type of ovarian tumor that has a benign nature.

**Why the Correct Answer is Right**
Fibromas are benign ovarian tumors that are most commonly associated with Meig's syndrome. These tumors typically arise from the ovarian stroma and are composed of fibrous tissue. The pathophysiology behind Meig's syndrome is thought to be related to the production of estrogen by the fibroma, which leads to fluid accumulation in the abdominal cavity and pleural space. The resolution of symptoms after tumor removal is likely due to the cessation of estrogen production and subsequent decrease in fluid production.

**Why Each Wrong Option is Incorrect**
**Option A:** Teratomas are a type of germ cell tumor that can be malignant and are not typically associated with Meig's syndrome.

**Option B:** Brenner tumors are a type of epithelial ovarian tumor that can be benign or malignant, but are not commonly linked to Meig's syndrome.

**Option D:** Theca cell tumors are a type of sex cord-stromal tumor that can produce estrogen, but are not typically associated with Meig's syndrome.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that Meig's syndrome is a rare clinical entity that is often associated with benign ovarian tumors, and the symptoms resolve after removal of the tumor. This distinction is critical in differentiating Meig's syndrome from other ovarian tumor-related complications.

**✓ Correct Answer: C. Fibroma**