"Useful primary source document" is the one among the following choices given in the question that <span>accurately describes a letter written during the time a historical event occurred. The correct option among all the options that are given in the question is the last option or option "e". I hope the answer helped you.</span>
<span>John D. Rockefeller did everything by his own. Vertical integrations means that he employed his own workers, then he constructed barrels to store oil and rent wagons and horses to transport that barrels. So it's called vertical integration. </span>
It was the Civil rights Act of 1866 that was passed by Congress to protect the voting rights of blacks in the South, although it wasn’t very effective, because it couldn't be enforced.
The two Germans who developed the economic and political philosophy known as communism are "<span>Marx and Engels", although these ideas quickly spread to Russia, which launched the Revolution of 1917. </span>
