Galactosemia Is a Metabolic Disorder Characterized by the Inability to Metabolize

Galactosemia is a metabolic disorder characterized by the inability to metabolize the sugar galactose.People with galactosemia suffer from liver, kidney, and brain damage among other symptoms.A gene mutation underlying galactosemia was identified by sequencing the genome of a person with galactosemia.What additional evidence would support the hypothesis that the mutation in the candidate gene causes the disease?

A) Observing that the genome of the person with galactosemia contains mutations in several other genes.
B) Collecting family history and determining that no other family members have galactosemia.
C) Sequencing the genomes from unrelated people with galactosemia and discovering that they also have mutations in the candidate gene.
D) Sequencing the genomes of family members without galactosemia and discovering that they also have mutations in the candidate gene.