**Core Concept**
Retinitis pigmentosa (RP) is a group of genetic disorders affecting the retina's rod photoreceptors, leading to progressive vision loss. The inheritance patterns of RP are diverse, but one pattern is more common than others.

**Why the Correct Answer is Right**
The most common inheritance pattern of retinitis pigmentosa is autosomal dominant. This means that a single copy of the mutated gene is sufficient to cause the condition, and each child of an affected parent has a 50% chance of inheriting the mutated gene. The dominant pattern is characterized by a wide range of mutations in the rhodopsin gene (RHO), the most common cause of autosomal dominant RP.

**Why Each Wrong Option is Incorrect**
**Option A:** Autosomal recessive RP is less common than autosomal dominant RP, accounting for approximately 10-20% of cases. While it does follow an autosomal recessive inheritance pattern, it is not the most common form.
**Option B:** X-linked RP accounts for a small percentage of cases, primarily affecting males due to the location of the mutated gene on the X chromosome. This is not the most common inheritance pattern.
**Option C:** Mitochondrial RP is caused by mutations in mitochondrial DNA and is maternally inherited. It is a rare form of RP and not the most common.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that RP can be caused by mutations in various genes, and each gene may have different inheritance patterns. A thorough family history and genetic testing are crucial for accurate diagnosis and counseling.

**Correct Answer: A. Autosomal dominant.**