**Question:** The local district magistrate's cou has asked your opinion regarding a paternity dispute. The alleged father is B+ and the mother is AB+. Which of the following groups would not be possible in their offspring?

A. AB-
B. AB+
C. A-
D. A+

**Core Concept:** Blood groups in humans are determined by the presence or absence of antigens on red blood cells. Antigens are substances that elicit an immune response. There are four main blood groups in humans: A, B, AB, and O. Antigen combinations lead to different blood types.

**Why the Correct Answer is Right:** When we consider the blood groups of the alleged father (B+) and the mother (AB+), we can determine the possible blood groups of their offspring by the following rules:

1. The offspring can inherit either the father's or the mother's blood group.
2. If the father is Rh positive (RhD+) and the mother is Rh positive, the offspring will be Rh positive.
3. The offspring will inherit one antigen from each parent (either A or B from the father, and either A or B from the mother).
4. The offspring cannot inherit both A and B antigens from the father and both A and B antigens from the mother.

**Why Each Wrong Option is Incorrect:**

A. **AB-**: Since the father is B+ and the mother is AB+, the offspring cannot inherit the A antigen from the mother and the B antigen from the father. This is because the mother is AB+, which means she has received antigens A and B from her parents. Only the father's antigens can be inherited.

B. **AB+**: This option is incorrect because the offspring cannot inherit both A and B antigens from the father and mother, as explained above.

C. **A-**: This option is incorrect because, as mentioned above, the offspring can inherit one antigen from each parent. The father is B+, so the offspring can inherit the A antigen from the mother.

D. **A+**: This option is incorrect because the offspring cannot inherit both A and B antigens from the father and mother, as explained above.

**Clinical Pearl:** Understanding blood group inheritance is essential in forensic medicine and paternity testing. Inheritance of blood groups follows the rules of Mendelian genetics, which can be confusing due to the presence of multiple antigens and the fact that the mother has received antigens A and B. However, by applying the rules explained above, we can determine the possible blood groups in the offspring.