A woman with a fourth blood group married a man with a second blood group. What blood groups can their

A woman with a fourth blood group married a man with a second blood group. What blood groups can their children have if, with a possible analyzing crossing of a man, half of the children would have a second blood group, half of the first blood group?

Since with a possible analyzing crossing of a man, half of the children would have the first blood group and half of the second blood group, it means that the man has the second blood group (heterozygote). A woman with a fourth blood group and a man with a second blood group (heterozygote) may have children with the second (both homozygote and heterozygote), third (heterozygote) and fourth blood groups.