If "Russia" is a referent, which of the following could be the concept?

A) CONTINENT
B) BORDER
C) MOSCOW
D) COUNTRY
E) EUROPE

Referent

The entity or item that is represented or signified by a word or expression.

Continent

A large continuous mass of land distinguished by geographers as one of the major landmasses on Earth's surface.

Country

A recognized political entity with its own government, territory, and population.