I'm pretty sure A is the secondary source. All of the others come directly from the source/person, but an interview is getting someone else's view.
I believe it is the 1st one but may be the 2nd one.
The correct answer is letter C.
Explanation: The British Empire was the largest empire in human history, dominating nearly a quarter of the planet.
The economic development in the 19th century, was because of the use of the slavers too. For the industrialists they were cheaper and offered a work, a good work for a good price.
