Final answer:
The Austro-Hungarian Empire consisted of a diverse population with various ethnicities. The percentage of Austrian or Hungarian citizens in the empire is uncertain.
Step-by-step explanation:
The Austro-Hungarian Empire was a multi-ethnic empire that included people of various nationalities. While it is difficult to determine the exact percentage of Austrian or Hungarian citizens, it is estimated that the majority of the empire's population consisted of ethnic groups other than Austrians and Hungarians. Therefore, it is safe to say that the correct answer is none of the given options: D. 100%.