The answer is D: The final couplet restates the speaker’s ideas in the three quatrains.
The Shakespearean sonnet is divided into four parts. The first three parts, called quatrains, are each four lines long, and they develop a certain sequence of metaphors or ideas, one per quatrain. The fourth part is called a couplet and it is two lines long and in this part the sonnet presents either a summary or a reformulation of the ideas presented in the previous three parts, often shedding new interpretative light on them.
