In Act 4 of Shakespeare's play "Macbeth," Macduff compares himself to birds at least twice. What are the purposes and effects of these comparisons?
a) The purpose is to emphasize Macduff's freedom, and the effect is to create a sense of liberation.
b) The purpose is to highlight Macduff's vulnerability, and the effect is to evoke sympathy.
c) The purpose is to underscore Macduff's determination, and the effect is to convey his resolve.
d) The purpose is to symbolize Macduff's cowardice, and the effect is to diminish his character.