<prompt> Barts hydrops fetalis is lethal because:Hb Barts cannot bind oxygenThe excess a-globin form insoluble precipitatesHb Barts cannot release oxygen to fetal tissuesMicrocytic red cells become trapped in the placental  <response>: c. Hb Barts cannot release oxygen to fetal tissuesRef: Nelsons 20e p 2349-2352, Ghai 8e p 341As Hb Barts consists of 4y chains, which have very high oxygen affinity, it cannot release oxygen to fetal tissues. 