Final answer:
The most prominent character transformation in 'The Fourteenth Goldfish' is Ellie's evolving perspective on aging and science as she learns from her youthful grandfather and develops a fascination with scientific discovery.
Step-by-step explanation:
The most prominent character transformation in "The Fourteenth Goldfish" by Jennifer L. Holm is Ellie's evolving perspective on aging and science. Throughout the story, Ellie interacts with her grandfather who has discovered the secret to eternal youth, which leads to her newly developed curiosity in science and a nuanced understanding of the aging process. This character development is central to the plot and underpins the novel's exploration of family dynamics, the implications of scientific discovery, and the acceptance of life's natural course.