**Core Concept**
Infertility is a complex disorder characterized by the inability to conceive after one year of unprotected intercourse. It is a multifactorial condition influenced by various physiological, anatomical, and pathological factors.

**Why the Correct Answer is Right**
Infertility can be caused by a variety of factors, including ovulatory disorders, such as polycystic ovary syndrome (PCOS), hypogonadotropic hypogonadism, and hyperprolactinemia. **Option C** is correct because it represents a common cause of infertility in women. PCOS is a leading cause of ovulatory dysfunction, resulting from insulin resistance, androgen excess, and ovarian stroma hyperplasia. It is characterized by irregular menstrual cycles, hyperandrogenism, and polycystic ovaries on ultrasound.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a specific cause of infertility and is too broad. While lifestyle factors, such as smoking and excessive alcohol consumption, can contribute to infertility, they are not the primary causes.
**Option B:** This option is incorrect because while endometriosis can cause infertility, it is not the most common cause. Endometriosis is a condition characterized by the growth of endometrial tissue outside the uterus, leading to inflammation, scarring, and adhesions that can affect ovulation and fertilization.

**Clinical Pearl / High-Yield Fact**
A key aspect of diagnosing and managing infertility is a thorough medical and reproductive history, including menstrual cycle regularity, duration of infertility, and previous pregnancy history. This information helps guide further evaluation and treatment.

**Correct Answer:** C. PCOS is a common cause of ovulatory dysfunction and infertility in women.