[A]: Erythroblastosis foetalis is a disease related with Rh factor and may cause death of foetus in the mother.
[R]: It causes massive destruction of foetal RBCs that leads to anaemia and tissue damage of foetus.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

**Step-by-Step Solution:**

1. **Understanding Erythroblastosis Foetalis**: Erythroblastosis foetalis is a medical condition that occurs when there is an incompatibility between the blood types of a mother and her fetus, specifically related to the Rh factor. This condition can lead to severe complications, including the death of the fetus.

2. **Role of Rh Factor**: The Rh factor is a specific protein found on the surface of red blood cells (RBCs). Individuals who have this protein are classified as Rh positive, while those who do not are classified as Rh negative.

3. **Mechanism of Erythroblastosis Foetalis**:
- If an Rh-negative mother becomes pregnant with an Rh-positive baby (inherited from an Rh-positive father), the mother’s immune system may recognize the Rh-positive blood cells as foreign.
- During delivery, some of the fetal blood can enter the mother's bloodstream, sensitizing her immune system to the Rh factor. The mother’s body then produces antibodies against Rh-positive blood cells.

4. **Impact on Subsequent Pregnancies**:
- In a subsequent pregnancy with another Rh-positive baby, the mother's pre-existing antibodies can cross the placenta and attack the fetal red blood cells, leading to their destruction.
- This results in anemia (a deficiency of red blood cells) and can cause significant tissue damage to the fetus, potentially leading to fetal death.

5. **Conclusion**:
- The assertion states that erythroblastosis foetalis is related to the Rh factor and may cause the death of the fetus, which is true.
- The reason provided states that it causes massive destruction of fetal RBCs, leading to anemia and tissue damage, which is also true and correctly explains the assertion.
- Therefore, both the assertion and reason are true, and the reason is the correct explanation of the assertion.

**Final Answer**: Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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