Which line in the following excerpt from joseph conrad’s heart of darkness indicate a flashback?

Pick One of these options. There can be more then one answer. These are the answers to your question.
1.)—"Mind, none of us would feel exactly like this. What saves us is efficiency—the devotion to efficiency. But these chaps were not much account, really.

2.) 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.

3.)He broke off. Flames glided in the river, small green flames, red flames, white flames, pursuing, overtaking, joining, crossing each other—then separating slowly or hastily.

4.) but it was only after a long silence, when he said, in a hesitating voice, "I suppose you fellows remember I did once turn fresh-water sailor for a bit," that we knew we were fated, before the ebb began to run, to hear about one of Marlow's inconclusive experiences.

His writing and speech is quite different than today’s. students struggle understanding because of unfamiliar words.