**Core Concept**
The lactiferous ducts are a vital part of the mammary gland, responsible for the transport of milk from the alveoli to the nipple. These ducts are lined with stratified squamous epithelium and are surrounded by smooth muscle, which helps in the contraction and relaxation of the ducts during milk ejection.

**Why the Correct Answer is Right**
The lactiferous ducts open into the nipple through small openings called duct orifices. There are approximately 15-20 lactiferous ducts that open into the nipple. Each duct has a separate orifice and is responsible for the secretion of milk from the corresponding lobule of the mammary gland. During lactation, the contraction of the smooth muscle surrounding the lactiferous ducts helps in the ejection of milk into the nipple, allowing the baby to feed.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the number of lactiferous ducts that open into the nipple is not 5. While there are indeed multiple ducts, the exact number can vary slightly from person to person, but it is generally agreed to be around 15-20.
* **Option B:** This option is incorrect because the number of lactiferous ducts that open into the nipple is not 25. While there are indeed multiple ducts, the exact number can vary slightly from person to person, but it is generally agreed to be around 15-20.
* **Option D:** This option is incorrect because the number of lactiferous ducts that open into the nipple is not 50. While there are indeed multiple ducts, the exact number can vary slightly from person to person, but it is generally agreed to be around 15-20.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the number of lactiferous ducts can vary slightly from person to person, but generally, there are around 15-20 ducts that open into the nipple. This knowledge is crucial for understanding the anatomy of the mammary gland and its function during lactation.

**Correct Answer: C. 15-20 lactiferous ducts open into the nipple.