**Core Concept**
Cicatricial entropion is a type of entropion characterized by the inversion of the eyelid margin due to scarring, often resulting from chronic conjunctival inflammation or previous eye surgery. The presence of Arlt line, a linear conjunctival scar, is a hallmark of this condition.

**Why the Correct Answer is Right**
The diagnosis of cicatricial entropion is supported by the presence of Arlt line, a linear conjunctival scar, which is a result of chronic trichiasis and subsequent scarring. Trichiasis is characterized by the inward turning of eyelashes, which can cause chronic irritation and inflammation of the cornea, leading to scarring and entropion.

* **Option A:** Ectropion is incorrect because ectropion is characterized by the eversion of the eyelid margin, which is the opposite of entropion.
* **Option B:** Mechanical entropion is incorrect because mechanical entropion is caused by mechanical factors such as eyelid retraction or facial nerve palsy, which do not involve scarring or inflammation.
* **Option C:** Congenital entropion is incorrect because congenital entropion is a rare condition present at birth, which does not involve scarring or inflammation.

**Clinical Pearl / High-Yield Fact**
Arlt line is a classic clinical finding in cicatricial entropion, and its presence should prompt further investigation into the underlying cause of the entropion, such as chronic trichiasis or previous eye surgery.

**Correct Answer:** C. Cicatricial entropion.