which of the following conditions cause erythroblastosis foetails?

Options

A. Mother Rh^(+ve)` and foetus`Rh^(-ve)`
B. Mother Rh^(-ve)` and foetus`Rh^(+ve)`
C. Both mother and foetus `(Rh^-ve)`
D. Both mother and foetus `(Rh^+ve)`

Answer

### Step-by-Step Solution:

1. **Understanding Erythroblastosis Fetalis**:
- Erythroblastosis fetalis is a condition characterized by the destruction of fetal red blood cells (RBCs) due to incompatibility between the blood types of the mother and the fetus.

2. **Identifying the Cause**:
- The primary cause of erythroblastosis fetalis is the incompatibility of the Rh factor between the mother and the fetus. The Rh factor can be either positive (+) or negative (-).

3. **Analyzing the Rh Factor Compatibility**:
- If the mother is Rh-negative and the fetus is Rh-positive, the mother's immune system may produce antibodies against the fetal RBCs, leading to hemolysis (destruction of RBCs).

4. **Evaluating the Options**:
- The question provides four conditions. We need to determine which condition involves a mother being Rh-negative and a fetus being Rh-positive, as this is the scenario that leads to erythroblastosis fetalis.

5. **Selecting the Correct Condition**:
- After evaluating the options, the correct condition that causes erythroblastosis fetalis is when the mother is Rh-negative and the fetus is Rh-positive.

### Conclusion:
- The condition that causes erythroblastosis fetalis is when the mother is Rh-negative and the fetus is Rh-positive.

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