Which weapon was a primary cause of the u. s entry into world war 1

German U-boats. The Germans sunk the passenger ship The Lusitania and continued to strike passenger ships despite warnings.

answer: born in saint-dié, in the vosges department, france, he studied law, and was called to the bar at paris in 1854,[2] but soon went into politics, contributing to various newspapers, particularly to le temps. he attacked the second french empire with great violence, directing his opposition especially against baron haussmann, prefect of the seine department. a series of his articles in le temps was later republished as the fantastic tales of haussmannlaxupa (1868).[2]

explanation: