The correct answer is B) Workers use dynamite on a cliff they don't need to destroy.
The detail from "Heart of Darkness" that shows the ineffectiveness of the colonizers is "Workers use dynamite on a cliff they don't need to destroy."
Joseph Conrad wrote "Heart of Darkness" in 1899. He was a Poland writer that expressed human suffering in his works. He later traveled the world and was impacted by what he saw in Congo, Africa. He witnessed the evils of man such as racism during his travels through the Congo River.