**Core Concept**
Achondroplasia is the most common cause of short-limbed dwarfism, resulting from mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. This condition is characterized by the substitution of glycine to arginine at position 380 in the FGFR3 protein, leading to its constitutive activation and subsequent inhibition of bone growth.

**Why the Correct Answer is Right**
The mode of inheritance for achondroplasia is autosomal dominant, meaning that a single copy of the mutated FGFR3 gene is sufficient to cause the condition. This is due to the dominant-negative effect of the mutated protein, which disrupts normal bone growth even when the normal allele is present. The FGFR3 gene is located on chromosome 4p16.3, and the mutation leads to the activation of the MAPK and PI3K signaling pathways, resulting in the inhibition of chondrocyte proliferation and differentiation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Autosomal recessive inheritance is incorrect because it would require two copies of the mutated gene (one from each parent) to express the condition, which is not the case for achondroplasia.
* **Option B:** X-linked dominant inheritance is incorrect because achondroplasia is not linked to the X chromosome and does not exhibit the characteristic X-linked pattern of inheritance.
* **Option D:** Mitochondrial inheritance is incorrect because achondroplasia is not caused by mutations in mitochondrial DNA and does not exhibit the characteristic mitochondrial inheritance pattern.

**Clinical Pearl / High-Yield Fact**
Achondroplasia is the most common cause of short-limbed dwarfism, and its diagnosis is often made based on clinical examination and radiographic findings. The condition is characterized by a distinctive "bee-stung" appearance of the face, macrocephaly, and shortening of the limbs.

**Correct Answer:** C. Autosomal dominant.