It is important because if the cause didn't happen the effect wouldn't exist
The right answer is D) threats to American security made by Germany.
Most Americans supported the Triple Entente or Allied Powers, at the outbreak of World War I. The, Wilson administration declared the nation neutral but allowed businesses to extend credit to the Allies to purchase food and military supplies. Americans were outraged by the Germans’ use of unlimited submarine warfare, especially after the 1915 sinking of the British liner Lusitania. In 1917 unrestricted submarine activity and the revelation of the Zimmermann telegram, in which the Germans sought to incite the Mexicans to wage war against the United States, led the United States to enter the Great War.
The common answer you'll get for this question is that the Taliban were a brutal islamic fundamentalists who suppressed their population and who harboured terrorists. And they did (probably the answer that you want). But the United States invasion of Afghanistan in 2003 had some very sinister sides to it- apart from the torture and violations of human rights. Prior to the Taliban's seizure of power, the pro-American government before them had granted Unocal, a US oil company based out of California, permission to pipeline oil from Azerbaijan. Interestingly Unocal donated to both George HW Bush's (1st Bush President) and his son's George W Bush's presidency campaigns and Bush Sr served on the board of the company after his presidency (basically earned lots of money from them) so if youre writing an essay on this topic, I'd recommened you add some of the stuff I said because it highlights a conflict of interest and will probably serve to balance your essay.
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A result of the exaggerated stories published by newspapers in the late 1800's was that political divisions, especially between the Democrats and Republicans leading up to the Civil War deepened greatly.