Which sentence belongs in the introduction of an argumentative essay? In 1869, construction was completed on the first railroad to cross the United States.
Large numbers of people moved from the farms to the cities, where the factory jobs were.
Opponents claim that the massive pollution and dangerous working conditions that were caused by the Industrial Revolution outweigh any benefits to the country.
In the late 1800s, the Industrial Revolution became one of the best things to ever happen to the United States, as it resulted in many new types of inventions and transportation.

i believe the answer is a

explanation:

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the correct answer is:   "   3.6 % " .

          →   the unemployment rate is:   " 3.6 % " .

explanation:

to calculate the "unemployment rate" :

the "unemployment rate"   =

  [# of people unemployed] /   [working age population]   * 100 %   ;

                =   [9 million] / [250 million]     *   100 % ;

    →     note:   the units of "million" cancel out;

                    since:   " {million} / {million} = 1 " ;

                =   (9 / 250)   * 100 %   ;

                = 0.036 * 100 % ;

                =   3.6 %

answer:   the unemployment rate is:   " 3.6 % " .