Answer:
A. African slavery
Explanation:
Although we know that slavery was an important part of British Empire it was not a part of their system after 1830s. To be precise in 1833, British Empire prohibited slave trade inside their domain. This was in important change, that rearranged the position of the whole Empire.
The History of the Standard Oil Company is a 1904 book by journalist Ida Tarbell. It is an exposé about the Standard Oil Company, run at the time by oil tycoon John D. Rockefeller, the richest figure in American history.
<span>The most dramatic change in agriculture in the South was the invention of the cotton gin.
True </span>
This is indeed the answer