The answer is A: Latitude Lines.
I believe the answer would be A. Increased support by the other western nations for the open door policy in China
As Mikhail Gorbachev was appointed as General Secretary of the Communist Party of the Soviet Union, this is, leader of the government, he offered to allow for more openness in the traditionally rigid and dictatorial Soviet regime through a series of policies called <em>Perestroika. </em>Abroad, the president of the United States politically and diplomatically pressed Gorbachev to carry out concrete actions in order to prove the sincerity of his intentions. For that reason, people all over the world demanded the end of the Soviet military intervention in Afghanistan, more civil rights for the Soviet citizens, the destruction of nuclear warheads, and echoing the general sentiment of the time, in a speech delivered by president Reagan in Berlin, near the Berlin Wall dividing the city into a capitalist section and a socialist one, he pronounced his famous words, "Mr. Gorbachev, tear down this wall!"
This would be the definition of an obligation.