It seems like the answer could be D, however, I'm not entirely sure <span />
Response:
"It was only after an extended silence that he spoke, in a tentative tone, "I suppose you guys recall I once briefly became a fresh-water sailor," which indicated we were destined, just before the tide began to recede, to learn about one of Marlow's unresolved encounters."
Clarification:
Flashback in literature signifies a moment when the story’s narrative shifts back to a previous point in time. This technique is commonly employed to illustrate past occurrences that provide significant background information.
In the provided excerpt, a flashback arises to remind the second character of his change in profession to a fresh-water sailor for a period before the twist of fate led them to hear about one of Marlow's ambiguous experiences.
The second option, hopefully, this assists you.