Final answer:
The law that expanded the FBI's surveillance capabilities after the 9/11 attacks is (a) The Patriot Act, which has led to debate over national security and civil liberties.
Step-by-step explanation:
The law passed by Congress following the 9/11 attacks which expanded the ability of the FBI to look into people's media use and tap their phones is known as The Patriot Act.
Officially titled as the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001, the Patriot Act significantly broadened the scope of the federal government's surveillance capabilities.
This act has been the subject of much debate between the need for increased national security and the protection of civil liberties, as it allowed for covert surveillance and the monitoring of electronic communications without a warrant in some circumstances.