Final answer:
PRISM collects data on U.S. citizens in the United States by gathering data from companies that participate.
Step-by-step explanation:
PRISM collects data on U.S. citizens in the United States primarily by gathering data from companies that participate. Through legal processes such as court orders, PRISM compels technology companies to provide access to user data including emails, search history, and IP addresses, among other information. This allows PRISM to collect and analyze large amounts of data on U.S. citizens for national security purposes.
Learn more about PRISM data collection on U.S. citizens