**Core Concept**
The periodontal ligament (PDL) is a fibrous connective tissue that plays a crucial role in the attachment and support of teeth within the jawbone. The PDL is composed of collagen fibers, blood vessels, and nerve endings, and its primary function is to transmit forces from the tooth to the surrounding bone.

**Why the Correct Answer is Right**
The periodontal ligament is approximately 0.1-0.2 mm in thickness, which is a critical dimension for its function. The PDL is composed of a complex arrangement of collagen fibers, including the principal fibers that run from the cementum of the tooth to the alveolar bone, as well as the oblique and transseptal fibers that provide additional support and stability. The precise thickness and arrangement of the PDL fibers are essential for the transmission of forces and the maintenance of periodontal health.

**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect because it does not accurately reflect the known dimensions of the periodontal ligament.
**Option B:** This option would be incorrect because it suggests a much thicker PDL than is actually present.
**Option C:** This option would be incorrect because it implies a much thinner PDL than is typically observed.

**Clinical Pearl / High-Yield Fact**
The periodontal ligament is a dynamic tissue that responds to changes in the forces applied to the tooth, and its thickness and arrangement can be altered by various factors, including orthodontic treatment and periodontal disease.

**Correct Answer: C. 0.1-0.2 mm.**