Final answer:
President Wilson suggests that uniting all nations as a single moral force through the League of Nations is the best way to maintain peace. The correct option is a.
Step-by-step explanation:
According to President Woodrow Wilson, the best way to keep peace in the world is to unite all nations as a single moral force through the League of Nations. He emphasized that the power of mankind and the united moral forces of the world should be mobilized to maintain international peace and security.
Wilson argued against the view that the United States might be at a disadvantage in the League, stating that the League's council can only adopt a policy with a unanimous vote, meaning no action could be taken without U.S. consent. The correct option is a.