**Core Concept**
The periodontal ligament (PDL) is a crucial structure that connects the tooth to the surrounding alveolar bone, playing a vital role in tooth support and periodontal health. Understanding the normal width of the PDL is essential in diagnosing and managing periodontal diseases.

**Why the Correct Answer is Right**
The correct answer is based on the histological characteristics of the PDL. The normal width of the PDL is typically around **0.15-0.20 mm**, which allows for a balance between tooth support and bone remodeling. This width is crucial for the maintenance of periodontal health, as excessive PDL width can lead to tooth mobility, while insufficient width can result in periodontal disease.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because a PDL width of **0.05-0.10 mm** is considered narrow and may be associated with periodontal disease.
* **Option B:** This option is incorrect because a PDL width of **0.25-0.30 mm** is considered wide and may lead to tooth mobility.
* **Option C:** This option is incorrect because a PDL width of **0.10-0.15 mm** is within the normal range, but it is not the most accurate answer.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the normal width of the PDL can vary slightly between individuals and between different teeth. However, a PDL width of **0.15-0.20 mm** is generally considered the gold standard for periodontal health.

**Correct Answer:** C. 0.10-0.15 mm