**Core Concept**
The Bartholin's gland, also known as the greater vestibular gland, is a small compound racemose gland located in the deep perineal pouch. It secretes fluid to lubricate the vaginal opening.

**Why the Correct Answer is Right**
The duct of the Bartholin's gland opens on the inner side of the labium minus, which is one of the two external female genital organs, also known as the vulva. This location is crucial for the gland's function in providing lubrication to the vaginal opening. The gland's secretions help maintain vaginal health and reduce friction during sexual intercourse. The Bartholin's gland plays a vital role in maintaining the integrity of the vulvar skin and mucosa.

**Why Each Wrong Option is Incorrect**
**Option A:** The duct of the Bartholin's gland does not open on the outer side of the labium minus. This option is incorrect as the gland's duct opens internally, not externally.
**Option B:** The duct of the Bartholin's gland does not open on the inner side of the labium majus. This option is incorrect as the gland's duct opens on the inner side of the labium minus, not the labium majus.
**Option C:** The duct of the Bartholin's gland does not open on the outer side of the labium majus. This option is incorrect as the gland's duct opens internally, not externally, and on the labium minus, not the labium majus.

**Clinical Pearl / High-Yield Fact**
It's essential to remember the location of the Bartholin's gland and its duct to diagnose and manage conditions such as Bartholin's cysts or abscesses, which can occur when the gland's duct becomes obstructed.

**✓ Correct Answer: D. On inner side of Labium minus**