Answer:
D. to show that the words are not part of the original quote
Step-by-step explanation:
Square brackets can be used within quotations to modify, edit, clarify the context or fit the information around it. Thus, the words "San Francisco" were not included in the original sentence made by the author or speaker. Instead, they were added between brackets inside the quotation to provide background information so that readers can understand what specific area the writer or speaker refers to.