**Core Concept:** Ovarian tumors are a diverse group of benign and malignant neoplasms that can cause various clinical symptoms and signs due to hormonal secretion. Virilization refers to the production of male sex hormones, such as testosterone, leading to characteristic symptoms and signs in women.

**Why the Correct Answer is Right:** Androgen-secreting tumors in females are usually benign, and the most common type is an ovarian theca cell tumor. These tumors arise from the cells that produce and secrete sex hormones, primarily androgens like testosterone. The correct answer (C) represents theca cell tumors, which are the most common cause of virilization in women due to androgen overproduction.

**Why Each Wrong Option is Incorrect:**
A. Ovarian endometrioid carcinoma (a malignant tumor) is not the primary cause of virilization in women, although it can occasionally produce androgens.
B. Granulosa cell tumors (benign or malignant) are also not the primary cause of virilization in women, as they usually produce estrogen and progesterone, not androgens.
D. Leydig cell tumors (malignant) are usually associated with precocious puberty in males, not virilization in females.

**Clinical Pearl / High-Yield Fact:**
Understanding the hormonal production patterns of different ovarian tumors is essential for accurate diagnosis and appropriate management of patients presenting with virilization symptoms. A thorough clinical history, physical examination, and hormonal testing are crucial for reaching a definitive diagnosis and guiding treatment decisions.