The American attitude shifted in favor of rights for Native Americans. This is based on "Polls showed that Americans believed in rights for Native Americans". Why it's not A is because it wasn't the polling that contributed to the act, but what the polls showed which is C.
Mass production of goods resulted in the use of mechanization to have an oversupply. Some labor work were replaced by machines, which created unemployment and change of needed skills for an upgrade. Common work can be done by machines while the craft was still handed down to skilled workers. There was a high demand for buying machines that can reproduce products faster.
Until April 6th, 1917, America was still a declared neutral state and she had tried to keep out of World War 1. However, she had economic relationships with nations involved in the war such as loans and financial support. American Secretary of State William Jennings opposed this financial support of warring nations, arguing that refusing to loan to any Allied nations in Europe would help to accelerate the end of the war. Even though President Wilson agreed at first, he retreated this when France argued that if it was not legal to take out credits from America, then it was not legal to buy American goods as well.
Regarding this, the American steel industry had faced declining profits during the Recession of 1913–1914. And when the war began in Europe, the increased demand for tools of war began a period of intensified productivity that relieved many U.S. industrial companies.
The answer is C. memphis and thebes