Everything was part of the colonial economic system: the overseas territories supplied raw materials to the metropolis and these often sold the manufactures they produced under a monopoly regime to their colonies. With the passage of time, these practices were banned in the different countries that carried them out. Or at least officially, since unofficially the slave trade continued well into the nineteenth century, practically until the last colonial territories obtained independence or achieved a more rigorous political status within the State than that of a mere colony.
"c. A narrative source" is what a historian would use to get a firsthand account of a past event, since in these sources (which are also primary sources) a person is giving a first-hand account of the event itself.
