Which of these was a factor in the United States entrance in World War I? A) the invasion of Poland B) Japan's invasion of China C) The Axis threat to the Panama Canal D) German unrestricted submarine warfare

It was only German unrestricted submarine warfare that directly contributed to American involvement in the war. It would take the bombing of Peal Harbor to completely bring the US into the war.

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francocanacari francocanacari · Answer 2 · 2019-04-05T14:06:32-04:00

The correct answer is D, as the German unrestricted submarine warfare was a factor in the United States entrance in World War I.

In April 1917 the United States declared war on the Central Powers, which gave the war a global character. However, its effects would not be felt until 1918. The sinking by a German submarine of the RMS Lusitania on May 7, 1915, where 128 Americans died had generated an anti-German popular feeling among Americans, but it was the German announcement of a submarine war "without restrictions" together with the confirmation of the authenticity of the Zimmermann telegram which caused a flow of anti-German sentiments in the United States, and was the trigger for its official entry into war on the side of the allies.