Answer: So shows a snowy dove trooping with crows.
Explanation: alliteration is a literary device that consists in the repetition of the beginning sounds of consecutive words, or words that are close to each other. In the given excerpt from William Shakespeare's "Romeo and Juliet" the line that contains alliteration is "So shows a snowy dove trooping with crows" because, as we can see there is a repetition in the "s" sound at the beginning of the words "so," "shows," and "snowy."