Aviation and Airport Security Practice Test.

International terrorism involves groups or individuals whose terrorist activities are foreign-based and directed by countries or groups outside of the United States. It is different from domestic terrorism, which involves extremist individuals or groups operating within a country's borders. Cyber terrorism involves the use of technology to spread and carry out terrorist actions, and environmental terrorism refers to acts of violence or destruction aimed at damaging the natural environment. Therefore, B is the best answer as it specifically mentions activities "transcending national boundaries," which is a key aspect of international terrorism.