$A$ person with antigens '$B$' in $RBC$ and antibodies '$a$' (anti-$A$) in the plasma belongs to the blood group

The most well-known blood grouping system is the $ABO$ system. It is named $ABO$ and not $ABC$ because the $\text{O}$ in it refers to having:

A child of a mother with blood group $A$ and a father with blood group $AB$ may have any one of the following blood groups except

In a normal human,to help the transport of $O_2$ and $CO_2$ properly,the blood is:

In a medicolegal case of accidental interchange between two babies in a hospital,the baby of blood group $A$ could not be rightly given to a couple with:

$A$ person with an unknown $ABO$ blood group has suffered a major accident and requires immediate blood transfusion. $A$ friend offers to donate blood and has a valid certificate of their blood group. Which blood group must the friend have to ensure safe donation to any recipient?