Senator Henry Cabot Lodge's compromise during the debate over the Treaty of Versailles primarily involved the idea reflected in option B. He added an amendment that specified that ratification of the treaty and membership in the League of Nations should not be tied together. Lodge was concerned about the League's potential implications for U.S. sovereignty and sought to set conditions that would protect American interests. Therefore, the correct answer is:
B. He added an amendment that said ratification of the treaty and membership in the League of Nations should not be tied together.