It seems that you have missed the necessary options for us to answer this question, so I had to look for it. Anyway, here is the answer. The line in the given excerpt from Joseph Conrad’s Heart of Darkness that indicates a flashback is this: They were conquerors, and for that you want only brute force—nothing to boast of, when you have it, since your strength is just an accident arising from the weakness of others. They grabbed what they could get for the sake of what was to be got.
