Answer: B. Grete might have remained as shy and immature as she was at the beginning of the story.
One of the most interesting characteristics of Gregor's metamorphosis is that, although he is the only character who has physically changed, it is this same change which triggered a transformation in the rest of his family.
By taking care of Gregor, Grete has become stronger and more confident. She has found a life outside of the house, and has become more independent and self-sufficient. The novel implies that the trigger for the change is Gregor's own transformation, and that without it, Grete was likely to remain as shy and immature as she was at the beginning of the book.
