Answer:
C. The volta introduces a new idea that indicates a shift in tone from the octave of the sonnet.
Step-by-step explanation:
This is the best explanation of the effect of the volta in this sonnet. The "volta" (Italian for "turn") is a change in thought or argument that takes place towards the end of a sonnet. In this case, most of the sonnet talks about ways in which the speaker feels unfortunate. However, the volta signals a change, as the speaker begins to concentrate in what makes him feel lucky. The reason for his change is the thought of having the love of his beloved.