It's rare, but can easily be explained by genetics.
The A positive parent could be AA or AO for blood group, and the O positive parent would have to be OO for blood group. Both parents would have to be heterozygous for rh factor, Rh+ Rh- . So the A negative child would have to have inherited an A and O allele from the parents, and an Rh- allele from both parents. This gives the phenotype of A negative.
it can be rare only
No, if both parents are type O, the child must be type O. However, since one parent is positive and the other is negative, the child could be either positive or negative.
yes, but rare.
yes, but rare.
Blood type and Rh factor do not affect the health of a child except in rare conditions, usually due to incompatibility with the mother and child when the father and are positive but the mother is negative.
yes there is but it is rare
rare
Yes, it is quite possible. It does require both parents to have AO(+-) genotypes, which is somewhat rare, however.
AB negative is the rarest.
In the ABO blood system, type O positive blood is common, about 36% of the population. 90% of the population is Kell negative. So no, it is not rare.
No. A child of A and O parents would have A or O. For the child to be AB the parents would have to be A and B Or at least one would have to be AB. The O parent cannot be the parent - you might want to follow up with your doctor for further testing.
The RH factor is inherited independently of the blood group. The parents have the most common Rh (positive) and it is also dominant over the Rh (negative) allele. Both carriers would have to carry the Rh- allele in order to produce and Rh- child. If this were the case a child from these parents would have a 25% chance of being Rh- and a 75% chance of being Rh+. The blood groups of the parents O and B are different. O is recessive to all other blood groups so the O parent carries two alleles for O and that is the only gene that parent can pass. The B parent could be BB or BO. If the B type parent is BB all children should have the B blood type. If the B type parent is BO then the chance of a child being B type is 50% and of being O type is 50% as well. (There are very rare exceptions to this inheritance pattern, such a chimerism that may result in a child that doesn't match this pattern).