Final answer:
Option B effectively illustrates the development of Eckles' character by showing his change from confidence to fear and uncertainty. The statement is "'Get me out of here,' said Eckels. 'It was never like this before. I was always sure I'd come through alive.'"
Step-by-step explanation:
The line from "A Sound of Thunder" that best develops Eckles' character is "'Get me out of here,' said Eckels. 'It was never like this before. I was always sure I'd come through alive.'" This line directly reflects Eckels' fear and uncertainty in facing the danger he encounters, which contrasts with his previous confidence. It shows a more vulnerable and frightened side of Eckles and develops his character as someone who is now unsure of his survival, contrary to his attitude before the encounter.