A nine month old boy of Sindhi parents presented to you with complaints of pregressive lethargy, irritability & pallor since 6 months of age. Examination revealed severe pallor. Investigation showed Hb–3.8 mg%; MCV–58 fl; MCH–19.4 pg/ cell.hood film shows osmotic fragility is normal (target cells normoblasts). X-ray skull shows expansion of erythroid marrow. Which of the following is the most likely diagnosis –