H5N1, a highly pathogenic avian influenza (HPAI) subtype, has been the strain most commonly linked to bird-flu outbreaks in poultry across India in recent years, and it has occasionally caused sporadic human infections too.
Its name comes from the two proteins on the virus's surface, haemagglutinin type 5 (H5) and neuraminidase type 1 (N1).
None of the other listed combinations correspond to the avian-influenza subtype behind India's recent bird-flu outbreaks, so H5N1 is correct.