The correct answer is A) trade sanctions.
The non-violent mean of coercion that the United States used then to promote democratic ideal in other countries is trade sanctions.
Trade sanctions are one of the most useful measures that the United States uses to punish other countries when those countries reject democratic ideals. That was the case with the government of South Africa and the segregationist policy of the apartheid. Or a most recent case with the government of Cuba. Trade restrictions limit the commerce of goods and services between the U.S. and other nations. These economic embargoes put restrictions in trade and financial aid.