Sita and Ram have their first child. Sita knows her blood type is A, but Ram does not know his blood type. However, Ram knows that both his mother and father have type B blood. The first child is a boy named Kush. Kush has type O blood. Sita and Ram do not understand how this happened. Which of the following is the best explanation?

Kush's blood type will need to be checked after his first month of life, if Sita and Ram want to know his blood type, as it takes about a month for the blood type to develop in a newborn child

Sita's genotype is AA and Ram's genotype is OO; thus, Kush expresses the O phenotype

Sita's genotype is AO and Ram's genotype is OO; thus, Kush expresses the O phenotype

Because Ram's parents are both type B, Ram is not Khush's father