In humans, having a widow's peak is the result of a dominant gene, and having a normal hairline is a recessive trait. A man who has a widow's peak is homozygous for the trait and has a child with a woman who has a normal hairline. Which of the following best describes the most likely appearance of their child's hairline?
Their child would have a normal hairline.
Their child would have a widow's peak if the mother is a carrier for the trait.
Their child would have a normal hairline if the father passes on the recessive allele.
Their child would have a widow's peak.