**Core Concept:** Dominant autosomal inheritance is a pattern of inheritance where a healthy parent carries a mutated gene and passes it on to all their offspring, resulting in affected individuals. In this case, the mother is the carrier of the mutated gene.

**Why the Correct Answer is Right:** In dominant autosomal inheritance, the mother has a single mutated gene (allele) that she received from her unaffected (heterozygous) parent. When she mates with a healthy (homozygous normal) partner, both children will inherit one mutated (A) and one normal (B) gene from their parents. As a result, they will be heterozygous (C) and possess the trait but remain asymptomatic. The third child inherits two mutated genes (D), becoming a homozygous carrier and expressing the disease.

**Why Each Wrong Option is Incorrect:**
A. Dominant autosomal inheritance is a correct option but is not specifically stated in the question.
B. Recessive autosomal inheritance is the pattern where both parents need to carry the mutated gene for the offspring to inherit the disease.
C. X-linked recessive inheritance is a pattern specific to genes linked to the X chromosome, where only female offspring inherit the condition.
D. In this case, the mother is assumed to be homozygous carrier (homozygous recessive) for the disease, making this option incorrect as well.

**Clinical Pearl:** Dominant autosomal inheritance is a common mode of inheritance for genetic disorders such as cystic fibrosis, sickle cell anemia, and Huntington's disease. Understanding inheritance patterns is crucial for genetic counseling, disease diagnosis, and gene carrier identification.

**Correct Answer:** A. Dominant autosomal inheritance