Microcytic anaemia with normal iron studies and Hb electrophoresis showing mostly HbF with absent HbA means no β-chains are being made, which points to β-thalassaemia major (homozygous). Electrophoresis in β-thalassaemia shows raised HbF and HbA2.

• Sickle cell anaemia would show HbS.
• Alpha-thalassaemia trait and hereditary spherocytosis do not abolish HbA.
• Caveat: the sources describe thalassaemia major as severe and transfusion-dependent from infancy, so an asymptomatic 30-year-old is inconsistent. The stem is probably a flawed recall, but A is the only option that fits the electrophoresis.