Final answer:
To filter an Email Performance Report for California activity, use the Smart List tab to set geographic location criteria.
Step-by-step explanation:
To filter an Email Performance Report to show only activity from people in California, you would change the settings in the Smart List tab. A Smart List allows you to segment the data based on specific criteria, such as geographic location. By setting up a filter within the Smart List, you can ensure that the report only includes data from the selected region, which in this case is California.