Which of the following is true of the ethnic composition of east asia? a. north and south korea have been ethnically distinct for many centuries.
b. japanese peoples are mainly descended from mainland asian populations.
c. the han chinese comprise more than 90 percent of china's population.
d. about 25 percent of mongolians are ethnic kazakhs.

The option about the ethnic composition of East Asia that is true is C. the Han Chinese comprise more than 90 percent of China's popiulation. Even today, they tend to call themselves by the name Han. A is incorrect because they were the same nation for many centuries. B is incorrect as they also come from island populations. D is incorrect because that number is much larger.