Explanation:

- Option 1: Japanese

- "Mein Kampf" was not written in Japanese. This was not a language widely associated with Hitler or the Nazi regime at the time.

- Option 2: English

- The book was translated into English, but it was not originally written in this language. English-speaking countries became aware of Hitler’s ideas through these translations.

- Option 3: German

- "Mein Kampf" was originally written in German. Adolf Hitler dictated the narrative to his deputy, Rudolf Hess, while in prison.

- German was Hitler’s native language, and it was the primary language of Nazi ideology.

- Option 4: French

- Like English, "Mein Kampf" was translated into French later on. However, it was not originally written in French.