Plz thx
what was the main reason the soviet union crumbled in the 1980s?

a. glasnost led to rebellion against communist rule around the world.
b. the soviet economy could not match the u. s. military spending while meeting citizens' demand for consumer goods.
c. policies introduced by mikhail gorbachev resulted in the soviet union losing it's main source of income.
d. the united states convinced soviet leaders to abandon communist economic policies.