A Man's Mother Died from Having the Neurodegenerative Genetic Disorder

A man's mother died from having the neurodegenerative genetic disorder Huntington's disease, which is caused by a dominant mutant allele that exhibits high penetrance.The man's daughter wants to be tested for the mutant gene, and he tells her not to bother because her probability of having the disease is zero.Is he telling her the truth? Choose the most accurate answer.(Outcome #IIIa)

A) No, her probability of having the mutant allele is 0.5 or 50%
B) We do not know whether he is telling the truth or not based on the information given.
C) Yes, his probability of having the disease is only 0.05 or 5% and is diluted to almost zero in his daughter.