<prompt> Bas hydrops fetalis is lethal because -Hb Bas cannot bind oxygenThe excess a - globin form insoluble precipitatesHb Bas cannot release oxygen to fetal tissuesMicrocytic red cells become trapped in the placental  <response>: Ans. is c i.e., Hb Bas cannot release oxygen to fetal tissues In the foetus excess gamma globin chains form tetramers Hb Bas with such high affinity for oxygen that they deliver almost no oxygen to tissues - Robbins o Clinically this condition manifests as hydrops fetalis and fetus shows features similar to those of erythroblastosis fetalis --- Severe pallor, Generalized edema, Massive hepatosplenomegaly 