(A) Zimmerman Telegram
(B) Unrestricted submarine warfare
(C) ** Member of the allies
(D) Lusitania sinking
EXPLANATIONS BELOW
Concept note-1: -Germany’s resumption of submarine attacks on passenger and merchant ships in 1917 became the primary motivation behind Wilson’s decision to lead the United States into World War I.
Concept note-2: -Isolationists believed that World War II was ultimately a dispute between foreign nations and that the United States had no good reason to get involved. The best policy, they claimed, was for the United States to build up its own defenses and avoid antagonizing either side.