What would be the blood group of a father who has a child suffering from erythroblastosis foetalis ?

Options

A. Father's blood group is definitely Rh-ve
B. Father's blood group is definitely Rh+be
C. Father's blood group may ne definitely Rh+ve or Rh-ve
D. Father's blood group is definitely O Rh-ve

Answer

To determine the blood group of a father whose child is suffering from erythroblastosis fetalis, we need to understand the genetic inheritance of the Rh factor.

### Step-by-Step Solution:

1. **Understanding Erythroblastosis Fetalis**:
- Erythroblastosis fetalis is a condition that occurs when there is an incompatibility between the blood types of the mother and the fetus, specifically concerning the Rh factor.

2. **Rh Factor Basics**:
- The Rh factor is a protein that can be present on the surface of red blood cells. If a person has this protein, they are considered Rh positive (Rh+). If they do not have it, they are Rh negative (Rh-).
- The Rh positive trait is dominant over the Rh negative trait.

3. **Mother's Blood Group**:
- In this scenario, we assume the mother is Rh negative (Rh-). This means she does not have the Rh protein on her red blood cells.

4. **Child's Blood Group**:
- The child suffering from erythroblastosis fetalis must be Rh positive (Rh+). This is because the presence of Rh+ blood in the fetus can trigger an immune response from the Rh- mother, leading to the production of antibodies against the Rh factor.

5. **Father's Blood Group**:
- Since the child is Rh positive, the father must have contributed the Rh positive trait. Therefore, the father must be Rh positive (Rh+). If the father were Rh negative (Rh-), the child could not be Rh positive, as two Rh negative parents can only produce Rh negative offspring.

6. **Conclusion**:
- Based on the above reasoning, the blood group of the father must be Rh positive (Rh+).

### Final Answer:
The father's blood group is definitely Rh positive.