Question

For a child having blood group B, if father has blood group A, what may be the blood group of the mother?
A. O or A
B. O
C. B or AB
D. B

Answer 1

A blood classification is a characterization of blood, in light of the presence and nonattendance of antibodies and acquired antigenic substances on the outside of red platelets. These antigens might be proteins, sugars, glycoproteins, or glycolipids, contingent upon the blood grouping framework.

Complete answer:
The above blood grouping system is based on ABO blood grouping. Humans and many other primates possess this system. There are four types such as A, B, AB, and O. The two antigens and two antibodies are responsible for the ABO grouping. The particular combination of these four types determines an individual's blood group type in most cases.
So, a father with A blood group can have two possible genotypes: ${I^A}{I^A}$ and ${I^A}{I^O}$

A child with a blood group A can have two possible genotypes: ${I^B}{I^B}$ and ${I^B}{I^O}$
Now, we know that the child inherits blood type either from mother or father, so here we can see that the blood group of father and child is different. This confirms that the child inherited the blood type from the mother. So, the blood type of the mother is either B or AB.

Crossing:
Parent generation: ${I^A}{I^O} \times {I^B}{I^B}$
Gametes: ${I^A}{I^O}$, ${I^B}{I^B}$

| ${I^A}$| ${I^O}$
---|---|---
${I^B}$| ${I^A}{I^B}$| ${I^B}{I^O}$
${I^B}$| ${I^A}{I^B}$| ${I^B}{I^O}$

F1 generation phenotypic ratio $=$ $1$ AB group $:$ $1$ B group
Hence, the correct answer is option (C).

Note: There is around $36$ blood grouping system. Thus, notwithstanding the ABO antigens and Rh antigens, numerous different antigens are communicated on the RBC surface film. For instance, an individual can be AB, D positive, and simultaneously M and N positive (MNS framework), K positive (Kell framework), Lea, or Leb negative (Lewis framework).