George Washington's greatest challenge at Valley Forge was keeping his army together. The morale of his army was dwindling and so it was a challenge for Washington to keep the army together. The correct option among all the options given in the question is the third option or option "C".
United States's foreign policy was isolationism until Pearl Harbor because the US tried to be more of a humanitarianism than imperialism. Also, after WW2, the US refused to join the League of Nations in order to prevent the US from becoming involved in foreign affairs.
