**Question:** Length of the nasolacrimal duct is about:

**Core Concept:**
The nasolacrimal duct is a part of the human anatomy that plays a crucial role in the drainage of tears from the lacrimal sac to the inferior meatus of the nose. It is essential to understand its length for proper assessment and management of tear drainage disorders.

**Why the Correct Answer is Right:**
The correct answer is D, which states that the length of the nasolacrimal duct is approximately 14mm. The nasolacrimal duct is approximately 14mm long, starting from the junction of the lacrimal sac and ending at the inferior meatus. Understanding this length helps in diagnosing and treating tear drainage disorders accurately, such as epiphora or blocked tear ducts.

**Why Each Wrong Option is Incorrect:**
A) The first option, 5mm, is too short, making it an incorrect estimate for the typical length of the nasolacrimal duct.
B) The second option, 20mm, is too long, which is not consistent with the actual length of the duct.
C) The third option, 7mm, is also too short and inaccurate for the actual length of the nasolacrimal duct.

**Clinical Pearl:**
Understanding the length of the nasolacrimal duct is crucial for diagnosing tear drainage disorders accurately. A proper clinical examination should include assessing the length of the duct during the evaluation of epiphora or blocked tear ducts, as the correct diagnosis and treatment depend on accurate measurements.

**Correct Answer:**
D) The length of the nasolacrimal duct is approximately 14mm.