Under the Foreign Intelligence Surveillance Act (FISA), the FBI can monitor communications without a warrant if both parties are non-U.S. citizens and the surveillance is conducted for intelligence purposes.

However, if one or both parties are U.S. citizens, the FBI would typically require a warrant under FISA or a separate court authorization, even in a short-term investigation.

FISA (1978) & Patriot Act (2001) – Provide legal authority for surveillance but impose restrictions on monitoring U.S. citizens.

Fourth Amendment (Privacy Rights) – Prevents warrantless wiretapping of U.S. citizens except in national security cases.

Snowden Leaks (2013) & Mass Surveillance Ethics – Raised concerns over the overreach of intelligence agencies in digital surveillance.

Deontological Ethics (Right to Privacy vs. National Security) – Governments must balance security concerns with individual privacy rights.

Relevant Ethical References in Technology:Thus, the correct answer is A. Calls between two non-U.S. citizens, as FISA allows warrantless surveillance in such cases.