A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the trait – blood group A or O – is dominant? Why or why not?

This information is not sufficient. This is because each individual is carrying two alleles and the recessive trait can occur only when alleles are similar.For considering a trait as dominant or recessive, data of three generations is required but here we have data of only two generations.