What Was the Primary Cause of the Economic Collapse of East

What was the primary cause of the economic collapse of East Germany the late 1980's?​

A) ​Concern over the weakening economy of the Soviet Union.
B) ​"Brain drain" as skilled workers fled to the West.
C) ​Unemployment and severe discontent.
D) ​Reunification with West Germany.
E) ​A shutdown of work by protesters inspired by Lech Walesa and Solidarity.