Final answer:
Without additional information on the query and the data structure, it's impossible to determine the number of rows returned simply from the amount of data processed. The correct answer is that it depends on the query.
Step-by-step explanation:
The question "You processed 415.8 GB of data. How many rows were returned by the query?" cannot be definitively answered with the information provided. The number of rows returned by a query is not directly related to the amount of data processed. Instead, the number of rows will depend on the specific structure of the database, the schema of the tables, the type of data stored, as well as what the query itself entails. Different types of data (text, images, numbers, etc.) and compression methods can also affect the size of the rows, and not all rows are the same size.
Therefore, the correct answer here is: B) Depends on the query. To determine the exact number of rows returned by a query, one would need more detailed information about the query's conditions and the data's structure.