Answer:
a. Hirohito was militarist; the others were nationalist.
Step-by-step explanation:
Indeed, among all the various options, the difference that is most likely is option a.
Remember, the term militarist is basically used to refer to someone who believes in building a very strong military strength for their country.
While the term nationalist is used to refer to someone who is extremely patriotic and would do everything they can to support their country's interests even though doing so could affect another country negatively.