I guess is A. The Marshall Plan.
I tried The Containment Policy and I got it wrong.
The primary reason why historians think this is because there has been discovered a single circulating currency in the region, that was used by people in different remote territories, implying that they were all working with a centralized economy.
The answer is B) Secularism.
Extensive political repression, a complete lack of democracy, widespread personality cultism, absolute control over the economy, massive censorship, mass surveillance, limited freedom of movement (most notably freedom to leave the country)