Class 11 NEET Biology Body Fluids and Circulation

Concept:Rh grouping is based on the presence or absence of Rh antigen on red blood cells, affecting pregnancy and blood transfusion compatibility.Key Fact:Erythroblastosis foetalis occurs when an $Rh^{-}$ mother carries an $Rh^{+}$ foetus, leading to immune sensitization after the first pregnancy.Explanation:Statement A is incorrect because the condition arises when the mother is $Rh^{-}$ and the foetus is $Rh^{+}$—not the reverse.Statement B is correct: about 80% of humans (Rh-positive) have the Rh antigen on RBCs.Statement C is correct: matching Rh group before transfusion prevents destruction of RBCs.Statement D is correct: Rh incompatibility is indeed observed when mother is $Rh^{-}$ and foetus is $Rh^{+}$.Statement E is incorrect: anti-Rh antibodies should be given to the mother immediately after delivery of the first child, not the second, to prevent sensitization for future pregnancies.Answer:The incorrect statements are A and E only, corresponding to option C.