**Core Concept**
Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive genetic disorders caused by mutations in the genes encoding enzymes involved in cortisol production, leading to cortisol deficiency and overproduction of androgens.

**Why the Correct Answer is Right**
The most common form of CAH is 21-hydroxylase deficiency, caused by mutations in the CYP21A2 gene. This enzyme is crucial for converting 17-hydroxyprogesterone to 11-deoxycortisol in the adrenal cortex. The autosomal recessive inheritance pattern means that an individual must inherit two defective copies of the gene (one from each parent) to express the condition. Carriers, who have one normal and one defective gene, typically do not display symptoms but can pass the defective gene to their offspring.

**Why Each Wrong Option is Incorrect**
**Option A:** X-linked inheritance - This is incorrect because CAH is caused by mutations in autosomal genes, not sex-linked genes.
**Option B:** Dominant inheritance - This is incorrect because CAH is caused by recessive mutations, and individuals with one normal gene cannot express the condition.
**Option C:** Mitochondrial inheritance - This is incorrect because CAH is caused by mutations in nuclear genes, not mitochondrial DNA.

**Clinical Pearl / High-Yield Fact**
CAH can be diagnosed prenatally through chorionic villus sampling (CVS) or amniocentesis, allowing for early management and potentially preventing life-threatening adrenal crises.

**Correct Answer: D. Autosomal recessive.**