What does the parenthetical phrase clarify in the article?

The correct response highlights that the parenthetical phrase is meant to modify the meaning of "jetties." In many texts, parenthetical phrases are included to provide additional information or context that enhances understanding. In this case, the phrase likely elaborates on what jetties are, perhaps describing their function, construction, or significance in relation to the main topic being discussed. This additional context helps readers grasp the concept more thoroughly and can clarify any potential ambiguities in the term itself.

Options that focus on definitions or comparisons may suggest supplementary information or explanations, but they do not capture the essence of how the phrase specifically alters or enhances the meaning of the term it follows. Thus, the modification aspect is crucial in understanding the role of the parenthetical phrase in the text.