Final answer:
The reporter experienced horizontal social mobility, which involves a career change without an accompanying change in social class or income.
Step-by-step explanation:
The reporter who changed careers from covering the police beat at a newspaper to becoming an editor of nonfiction books, while receiving the same salary, has experienced c. horizontal social mobility. This type of mobility refers to changes in a person's occupation or role that do not necessarily come with a higher or lower social status or income. Since the reporter is earning the same salary, despite the career change, there is no upward or downward shift in social class.