Haemophilia Is Caused by an X-Linked Recessive Mutation in Humans

Multiple Choice

Haemophilia is caused by an X-linked recessive mutation in humans.If a woman whose paternal uncle (father's brother) was a haemophiliac marries a man whose brother is also a haemophiliac,what is the probability of their first child having haemophilia? Assume that there are no other cases of haemophilia in the pedigree and no hidden carriers.

A) 0
B) 1/4
C) 1/2
D) 1/8
E) 1