Pedigrees are used to geneticists understand how traits are inherited between generations. the romanovs, a russian royal family, had a history of hemophilia, a sex-linked disorder that is determined by a recessive allele on the x chromosome.

what is the best evidence to prove that irene was heterozygous for hemophilia?

alice has the recessive allele.
alexandra has the recessive allele.
frederick has the recessive allele.
waldemar has the recessive allele.