1. A new competitor of Quanjude, SuperDuck, has become highly successful through its menu based solely on organically-raised duck, and other dishes' ingredients such as chicken, beef, and seasonal produce. SuperDuck has opened new locations in Shanghai, Chongqing, and other cities, and these new locations are becoming highly profitable. SuperDuck can expect that, at best, its competitive advantage will be

a.	permanent.
b.	sustainable.
c.	temporary.
d.	defensible.