**Core Concept**
The vulva contains several important structures, including the Bartholin's glands, which play a crucial role in vaginal lubrication. The Bartholin's glands, also known as the greater vestibular glands, are a pair of compound racemose glands located in the deep perineal pouch.

**Why the Correct Answer is Right**
The Bartholin's glands secrete a fluid that helps to lubricate the vagina. This fluid is released through the Bartholin's ducts, which open into the vaginal vestibule, a region of skin that surrounds the opening of the vagina. The Bartholin's glands are innervated by the pudendal nerve and are under the control of the sympathetic nervous system. The secretion of the Bartholin's glands is essential for vaginal lubrication and helps to reduce friction during sexual intercourse.

**Why Each Wrong Option is Incorrect**
* **Option A:** The Bartholin's ducts do not open into the urethra. The urethra is a separate structure that carries urine from the bladder to the outside of the body.
* **Option B:** The Bartholin's ducts do not open into the clitoris. The clitoris is a highly innervated structure that plays a key role in female sexual arousal, but it is not directly related to the Bartholin's glands.
* **Option C:** The Bartholin's ducts do not open into the labia majora. While the labia majora are part of the vulva, they are not the correct location for the opening of the Bartholin's ducts.

**Clinical Pearl / High-Yield Fact**
The Bartholin's glands can become inflamed or infected, leading to a condition known as Bartholin's cyst or abscess. This can cause significant pain and discomfort, and may require surgical drainage or other treatment.

**Correct Answer: C. Vaginal vestibule**