**Core Concept**
The **periodontal ligament** and its associated **gingival fibres** play a crucial role in the support and stability of teeth within the jaw. These fibres are classified based on their orientation and the structures they connect. The **gingival fibre group** is one such classification, which further divides into subgroups based on their insertion points.

**Why the Correct Answer is Right**
The correct answer is related to the specific subgroup of gingival fibres that insert into two adjacent teeth, providing support and stability to the teeth by connecting them. This subgroup is known for its role in maintaining the integrity of the **dental arch** and facilitating the distribution of forces during **mastication**.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the subgroup of gingival fibres that insert into two adjacent teeth.
**Option B:** Similarly, this option does not correctly identify the specific subgroup of gingival fibres in question.
**Option D:** This option is also incorrect as it does not correspond to the subgroup of gingival fibres that connect two adjacent teeth.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that the health and arrangement of gingival fibres are vital for **periodontal health** and the overall stability of the teeth. Any disruption in these fibres can lead to **periodontal disease** and potentially severe consequences for dental health.

**Correct Answer:** C. Interdental fibres.