The correct answer is A. Isolationism.
Isolationism is a foreign policy strategy that asserts to not intervene in foreign affairs that do not imply a real threat to the country. This policy limits the participation of a particular state in the international arena in order to avoid unnecessary conflicts or undesirable political, economic, or cultural influences. Different countries have taken Isolationism as a main foreign policy throughout history, like China during the Ming dynasty in the 15th century and the US during the 19th century.