Why didn't the two sons of Queen Victoria (Alfred and Arthur) display hemophilia? (refer to pedigree chart)
because they are only carrying one recessive gene (b)
because their father did not have the trait
because they received the dominant gene "Y" from their father
because they did not receive the recessive gene (Xb) from their mother.

Why didn't Charles and Alexander, the grandsons of Queen Victoria receive hemophilia from their father Leopold?
because the disease is not carried on the "Y" chromosome
because Helena does not carry the trait
because Helena carries the trait but it is not homozygous
because the disease is not on the "Y" chromosome and Helena did not have the trait