The most accurate words to fill the spaces would be:
Sugar plantations were the backbone ( source ) of the economy.
In 1890, the US Congress passed the ( McKinley Tariff ), which removed tariffs on all foreign sugar imports.
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Working for the following establish
Try googling it cuz those are paragraphs
The only reason why African slavery was so popular is that The cost of a white man's labor for 10 years could buy an African for life, so it's the third option represented above. There was no lack of native people or moral issues,so the price, which was established, lead to such situation.
