<em>Twilight</em> is the metaphor for aging that Shakespeare uses. In a metaphor, there is a hidden comparison between two things that are not related but that share some characteristics. Metaphors leave out the words "like" and "as" that are used in similies. One of the themes that Shakespeare addresses in his sonnets is love and beauty. The other theme that is repeated in Shakespeare's sonnets is the passing of time, the way youth fades and old age comes. Art as a way of immortalizing beauty.
Twilight is the metaphor for aginf tha Shakespeare uses. Option C is correct.
A metaphor is understood as a figure of speech that describes an object or action in a way that isn’t literally true, but helps convey an idea or draw a comparison.
A metaphor states that one thing is another thing.
Metaphors are used in poetry, literature.
So, this literary decive is implemented in order to encourage the reader to make a comparison between two seemingly unrelated things.