**Core Concept**
The management of polycystic ovary syndrome (PCOS) often involves the use of medications to induce ovulation and regulate menstrual cycles. In PCOS, anovulation is a common feature, and follicle induction is a key treatment goal.

**Why the Correct Answer is Right**
Clomiphene citrate is a selective estrogen receptor modulator (SERM) that acts by binding to estrogen receptors in the hypothalamus, leading to an increase in gonadotropin-releasing hormone (GnRH) and subsequently luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release. This increase in gonadotropins stimulates follicular growth, making clomiphene citrate a first-line treatment for inducing ovulation in women with PCOS.

**Why Each Wrong Option is Incorrect**
**Option A:** Letrozole is another option for ovulation induction, but it is not the first-line treatment. Letrozole is an aromatase inhibitor that decreases estrogen levels, leading to an increase in FSH release.
**Option B:** Metformin is used to treat insulin resistance in PCOS but is not a first-line treatment for ovulation induction. It works by decreasing insulin levels, which can improve ovulation.
**Option C:** Gonadotropins are used in cases of clomiphene resistance or failure but are not the first-line treatment due to their higher cost and risk of ovarian hyperstimulation syndrome.

**Clinical Pearl / High-Yield Fact**
Remember that clomiphene citrate should be started on day 5 of the menstrual cycle to ensure ovulation occurs during the luteal phase, which is crucial for successful implantation and pregnancy.

**Correct Answer: C. Clomiphene citrate**