Korea is a good example of a(n)
a. sovereign state
b. nation-state existing in a unified condition.
c. ethnicity divided between more than one state.
d. colony divided between more than one ethnicity.
e. patron-state

c.ethnicity divided between more than one state.

Explanation:

Korea is an East Asian nation and is located on the southern Korean peninsular and shares one of the heavily metalized borders.  And is divided into more than one state and southern and the western parts of the nations and they belong to the East Asian nations.Plus they have a number of the native southwestern Manchurian ethnic groups and lives in the north and south Korea and along with the ethnic minority of china and japan and the Philippines etc.  As of the 2020, there are estimated more than 8.3 million ethnic Koreans population.

81 is a composite number

Answer(a); // soil salinization and waterlogging;