Unrestricted submarine warfare, which became prominent in World War I, meant that submarines could sink any time of vessel at any time without warning. Before this, they had to surface first and place crews on lifeboats.
Approving international treaties is an exclusive power to the Senate.
I'd say (B) but I'm not completely sure.
B.
Hitler's main reason for starting World War II was the following:
He wanted to unite the German people
He wanted to expand the land of Germany to feed more people (this is why he demanded Danzig from Poland)
He restored the morale of the Continental Army in addition to introducing discipline and putting the tattered soldiers into fighting shape. He drilled the troops which were often in bad shape and defeated which was vital in helping the Continental Army accomplish its missions.
