Final answer:
The line that exemplifies foreshadowing is D) "If only I could have stopped her; if only I could have stopped him..." as it suggests future regret and consequences, indicative of foreshadowing in literature.
Step-by-step explanation:
The line that stands as an example of foreshadowing is D) "If only I could have stopped her; if only I could have stopped him..." This line suggests a future regret or consequence resulting from actions not taken, which is the essence of foreshadowing. A) describes a past event, B) is a metaphor, and C) is a plea, none of which indicate a future event. By using foreshadowing, authors create anticipation in the narrative, hinting at what is to come without revealing the story.