The incidents from Frankenstein that most clearly develop a theme related to the pursuit of knowledge is option C. Victor attempts to discover the secret of life, and Walton searches for a northern passage to the Pacific Ocean.
One of the major themes of the novel Frankenstein by Mary Shelley is the dangers of the over-reaching pursuit of knowledge.
Regarding this theme, Mary Shelley focused on the fact that inventors and scientists have generally always been praised for their discoveries, even though some portions of the population worried, and continue to do so, about the extent in which people are willing to go for such knowledge.