**Core Concept**
Familial retinoblastomas are a type of cancer that primarily affects the retina of the eye. The inheritance pattern of this condition is a classic example of a genetic disorder.

**Why the Correct Answer is Right**
Familial retinoblastomas are caused by a mutation in the RB1 gene, which is located on chromosome 13. This gene acts as a tumor suppressor, and when it is mutated, it can lead to the development of retinoblastomas. The inheritance pattern of familial retinoblastomas is autosomal dominant, meaning that a single copy of the mutated gene is sufficient to cause the condition. This means that if one parent has the mutated gene, each child has a 50% chance of inheriting it.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because familial retinoblastomas are not caused by a mutation in a gene that is linked to sex chromosomes.
**Option B:** This option is incorrect because the inheritance pattern of familial retinoblastomas is not X-linked dominant, which would require two copies of the mutated gene (one from each parent) to cause the condition.
**Option C:** This option is incorrect because the inheritance pattern of familial retinoblastomas is not autosomal recessive, which would require two copies of the mutated gene (one from each parent) to cause the condition.

**Clinical Pearl / High-Yield Fact**
The RB1 gene is a classic example of a tumor suppressor gene, and mutations in this gene can lead to the development of various types of cancer, including retinoblastomas, osteosarcomas, and soft tissue sarcomas.

**Correct Answer: D. Autosomal dominant.**