I believe the answer is C. But I am not quite sure
The correct answer is sentence (5).
A sentence fragment means that it is only a part of a sentence; it is not complete. Given that it is incomplete, the fragment, aka subordinate/dependent sentence, has to be part of a larger, independent sentence, in order to make any sense. So if you combined sentence (5) with another one, it wouldn't be a fragment anymore.
Robert Browning's "My Last Duchess" does not rely heavily on metaphors. It is rather a monologue delivered by the speaker describing a painting of his wife and his wife as a person when she was still living. The painting can be said to symbolize the wife, the last duchess. There are a few metaphors sprinkled throughout the poem, though, as the speaker paints a verbal portrait of his former wife.
When the speaker says in lines 1-2 "That’s my last Duchess painted on the wall, / Looking as if she were alive," his choice of words could be considered metaphorical. The duchess herself is not literally on the wall; rather, this is a painting or a likeness of her, which stands in for her throughout the poem. One of the few metaphors in the poem is the "spot of joy" referenced by the speaker. The speaker suggests that most people wonder what exactly makes his lady smile and appear happy in the painting.
