Cystic fibrosis is an autosomal recessive trait characterized by abnormally viscous mucus in the lungs and digestive system.

• A. Hemophilia
• B. X-linked disorders
• C. Cystic fibrosis
• D. Huntington disease

Answer: (C)

This item tests understanding of autosomal recessive inheritance and how a disease’s description matches that pattern. In autosomal recessive conditions, two mutated copies of the gene are needed for the disease to manifest, so affected individuals are usually from carrier-by-carrier matings, and both males and females are affected with similar frequency. Cystic fibrosis fits this pattern because it is caused by mutations in the CFTR gene on an autosome, and its hallmark is abnormally viscous mucus in the lungs and digestive system due to defective chloride transport.

The other options don’t fit the given description. Hemophilia is typically X-linked recessive, affecting males more often and not described by an autosomal pattern. Huntington disease is autosomal dominant and often has a later onset, which contradicts the stated inheritance pattern. Labeling the disorder category as X-linked disorders or autosomal dominant would also clash with the specific autosomal recessive trait described.

So, cystic fibrosis is the best match because it aligns with autosomal recessive inheritance and the described mucus-related organ system involvement.