Huntington's disease is an autosomal dominant disorder that affects the nervous system. if a man is heterozygous for the alleles that cause the condition and has children with a women who lacks that defective allele, which of these statements is true?

Huntington's disease is a disease that inherited autosomal dominant. That means you just need one allele to made it expressed. Let say that H is Huntington's allele and N is normal allele. In this case, the heterozygous father has (H x N) gene and the normal mother has (N x N) gene.

That mean
1. The father will have 50% chance to give normal allele and 50% chance to give H allele
2. The mother will have 100% chance to give N allele

Since you just need 1 H allele to got Huntington's disease, 50% the children will have Huntington's while 50% of them is normal

Olfactory epithelium i believe