which of the following events is an example of arbitration?

a. NATO passes a resolution against Iran.
b. The United States set up a meeting between Taiwan in China.
c. After hearing both sides, the United States decides to end the Russian occupation of Crimea.
d. Opposing factions in the second Congo war meet at the neutral African union headquarters.

d. Opposing factions in the second Congo war meet at the neutral African union headquarters.