Answer:
the answer is D.
Explanation: During the first year of world war 1 America remained neutral from European war. But the situation became critical when Germany was responsible for sinking British cruiser Lusitania . After that the state secretary sent a soft message to the German authority from US. But in the second letter President Wilson sent a strong warning to Germany. Jenning thought it was a indication for US to get involved in the war. So for this reason he resigned from his post.