A nation engaged in war cannot attain high levels of excellence in cultural fields.

Answer: Option B

One word substitute is Belligerent.

Bellicose: demonstrating aggression and willingness to fight.
Belligerent: engaged in a war or conflict, as recognized by international law.
Imperialist: relating to, supporting, or practising imperialism.
Courageous: not deterred by danger or pain; brave.