New mutations can also occur randomly, so there’s a chance that children of parents who didn’t inherit the gene for Huntington’s can develop a mutation in the gene that causes Huntington’s disease explain how protein synthesis contributes to the symptoms of the disease

It depends on the mutation rate  

Explanation:

Mutations are genetic changes that occur naturally by errors during DNA replication which are not repaired by the DNA repair mechanisms. When a mutation occurs in the germline line, it may pass to the next generations and thus perpetuate itself. Huntington's disorder is an autosomal dominant disorder associated with a trinucleotide repeat mutation in the huntingtin (HTT) gene localized on chromosome 4, which encodes the Huntingtin protein. It has been shown that the high levels of Huntingtin are linked to Huntington's disorder, thereby it is believed that this mutation might be associated with a higher expression of the HTT gene.

i think the answer would be d