Nationalism, a strong sense of love and devotion toward a nation, can lead to another step in a nation's growth,
a. war
b. economic growth
c. greater cultural awareness
d. self-rule

Nationalism can inspire people to pursue self-rule when a nation is not independent such as in the case of the Kurdish people. however, typically a nation is independent already.
I would say that a greater cultural awareness is the best a answer- it's a positive factor so it can be understood as the nation's growth.

Nationalism can also lead to wars, but that's not a growth