Which of the following is the flightless bird?

A. Pavo cristatus
B. kakapo
C. Passer
D. None of these

The kakapo, also called owl parrot, is a species of large, flightless, nocturnal, ground-dwelling parrot of the super-family Strigopoidea, endemic to New Zealand. It has finely blotched yellow-green plumage, a distinct facial disc, a large grey beak, short legs, large feet, and relatively short wings and tail.
Some other flightless birds you might  know are. Emu, dodo, emperor penguin,  little penguin & common ostrich.