Final answer:
Japan is known for its ethnic homogeneity, with nearly all of its population being ethnically Japanese, embodying a nation-state with strong centripetal forces.
Step-by-step explanation:
Comparing Australia's ethnic diversity to that of Japan, we find notable differences. Japan is known for its ethnic homogeneity.
In fact, in 2010, all but 1 percent of the population was ethnically Japanese, indicating a very high level of ethnic unity. This creates strong centripetal forces that unify the nation.
Conversely, Australia's proximity to Asia and its evolving immigration patterns have contributed to its increasing ethnic diversity. Although historically the Australian government has implemented policies to maintain a European majority, the growing presence of Asians and other ethnicities is evident.
This shift demonstrates that Australia is becoming less culturally isolated and more diverse.
Furthermore, within both countries, varied religious dynamics suggest the existence of some level of cultural diversity.
However, the ethnic diversity in Australia, influenced by its immigration and proximity to the Asian realm, is more pronounced compared to Japan's homogeneity.
As such, Japan has less ethnic diversity than Australia, which has ongoing immigration and a growing multicultural society. Answer choice D is therefore the correct one: Japan is less ethnically diverse than Australia.