Huntington's Disease Problem

A man whose father was diagnosed with the dominant Huntington Disease (HD) marries a woman whose family has no history of the disease. In his early thirties, the man is also diagnosed with HD. What is the probability that the couple's second child will develop HD?

a couple problems with this question... there is no mention of the man's mother's genotype, which makes no sense since that can completely change the outcome of this problem. I drew out a pedigree chart... dominant HD for dad could mean he is either a heterozygote for the disease or a homozygous dominant, which leads to two completely different answers. and the man marrying a woman unaffected by the disease means either the kids are heterozygotes for HD or they could be 50/50 having and not having.   The answer choices are: 0, 1/16, 1/4, 1/2, 3/4, 1.

Where am i going wrong here?