What blood types are possible among the children of a cross between a man of blood-type a and a woman of blood-type b?

Depends on the genotype of the parents the child could be any blood type A,B,AB,O. Blood type A & B are dominant over O , so the parents could be heterozygous (genotype AO & BO, they have each the allele for the recessive blood O) and homozygous (genotype AA & BB).

# If the both parents have homozygous (genotype AA & BB) than the offspring will be blood type AB.

# If the parents have heterozygous (AO & BO) then the offspring will be A,B,AB,O.

# If the genotype of parents are AO & BB then the offspring will be AB, B.

# If the genotype of parents are AA &

BO then the offspring will be AB , A.

a time line cause it goes from 685 to 978