**Core Concept**
The Wolffian ducts are a pair of embryonic structures that develop into the male reproductive system, including the epididymis, vas deferens, seminal vesicles, and prostate. In females, these ducts regress due to the absence of androgens, but remnants may persist and give rise to various congenital anomalies.

**Why the Correct Answer is Right**
The correct answer is related to the embryological development of the female reproductive system. In females, the Wolffian ducts regress due to the lack of androgens, but remnants may persist and give rise to structures such as the epoophoron, paroophoron, and Gartner's duct. These remnants are vestigial structures that are remnants of the Wolffian ducts.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the remnants of Wolffian ducts in females.
**Option B:** This option is incorrect because it refers to a different embryological structure altogether.
**Option C:** This option is incorrect because it is not a recognized remnant of the Wolffian ducts in females.
**Option D:** This option is incorrect because it is a characteristic of the female reproductive system, not a remnant of the Wolffian ducts.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that remnants of the Wolffian ducts can give rise to various congenital anomalies, including cysts and ductal ectasia, which can be mistaken for other conditions.

**Correct Answer: D. Para-ovarian cyst.