1. The Sudetenland issue, which led to the calling of the Munich Conference of 1938, centered on A. Hitler's introduction of German troops into the demilitarized Rhineland.
B. territory disputed between Germany and Poland.
C. ethnic Germans in the western region of Czechoslovakia.
D. the unification of Germany and Austria.

C. Ethnic Germans in the western region of Czechoslovakia

Explanation:

Hitler had pressured the Czechoslovakian government by demanding for the Sudetenland. The calling for the Munich Conference was to hopefully compromise for peace in exchange for the Sudetenland.

the treaty of brest-litovsk was a peace treaty signed on 3 march 1918 between the new bolshevik government of russia and the central powers (german empire, austria-hungary, bulgaria, and the ottoman empire), that ended russia's participation in world war i.