The correct option is C Palaeognathae
Palaeognathae are one of the two living clade of birds (the other is Neognathae). Palaeognathae contains five extant branches of flightless lineages and one flying lineage. Palaeognathae includes largest living bird i.e., Ostrich. They are characterized by the primitive internal skull morphology and absence of kneel on sternum (therefore flightless).
Thus, the correct answer is option A.