**Core Concept**
Achondroplasia is a genetic disorder that affects bone growth, resulting in short stature. It is the most common form of short-limbed dwarfism. The underlying cause is a mutation in the **FGFR3** gene, which codes for the fibroblast growth factor receptor 3.

**Why the Correct Answer is Right**
The most common inheritance pattern of achondroplasia is autosomal dominant, meaning a single copy of the mutated gene is sufficient to cause the condition. Approximately 80% of cases are due to de novo mutations, while 20% are inherited from an affected parent. The **FGFR3** gene mutation leads to overactive signaling, resulting in impaired bone growth.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while some cases may be sporadic, the question asks for the most common inheritance pattern.
**Option B:** Incorrect as achondroplasia does not typically follow an autosomal recessive pattern.
**Option C:** Incorrect because X-linked inheritance is not characteristic of achondroplasia.
**Option D:** Incorrect as mitochondrial inheritance is not relevant to achondroplasia.

**Clinical Pearl / High-Yield Fact**
Achondroplasia is a classic example of an autosomal dominant disorder, and its diagnosis can be made based on clinical features and confirmed by genetic testing.

**Correct Answer:** C. Autosomal dominant