D- could not be, this did not happen until 1979.
among the three remaining ones I think that the best option is <span>c. Women's entrance into the workforce during World War I- this gave the women the power of persuasion</span>
The south improvement company in 1872 caused rockefeller able to monopolized around 90% of the oil market in North America.
The south improvement company largely increased the number of oil and railroad companies in southern states. Because of the increase in numbers, the market for oil and railroad companies became saturated. This lead many of his competitors to bankruptcy, which is why the competitors called it a conspiracy.
