Why were european nations able to conquer large sections of africa in the 19th and early 20th centuries?

"Why were European nations able to conquer large sections of Africa in the 19th and early 20th centuries? ... Europeans easily adapted to African climate and topography. 2. Europeans possessed more advanced military technology."

while it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton.

explanation:

before eli whitney's invention of the cotton gin, picking and cleaning cotton was a slow, labor-intensive job. workers, usually slaves, had to pick the seeds from the cotton fibers by hand. this invention made it possible to grow large amounts of cotton on big farms and make money.