Question

The powder keg of Europe refers to:

Answer 1

I think it might be d but please let me know if it is right

Answer 2

D) all of the choices are correct

political unrest = (explosion of the powder keg, as they were used for muskets)
nationalistic fervor = (usage in the military, which gives off a national feeling)
vying for power = (as the powder keg was used in military, it shows strength in the military)

hope this helps