Answer:
C. It demonstrates Frantz's realization that books are more important than anything else.
Step-by-step explanation:
The whole sentence with the underlining: "My books, which only a moment before I thought so tiresome, so heavy to carry—my grammar, my sacred history—seemed to me now like old friends, from whom I should be terribly grieved to part." The most related answer to this was C which is that until now that he realized that books are more important than anything else. In the previous sentence, he also stated how angry he was with him self because of the time he had wasted, the lessons he had missed,... to show that to now he has realized the answer was C.