Which of the following has NOT been targeted by terrorists?

The answer indicates that all the provided options—government buildings, public transportation systems, and religious gatherings—have indeed been targeted by terrorists in various incidents throughout history. This reflects the reality that terrorist organizations frequently choose targets that maximize visibility, impact, and psychological effects on the population.

Government buildings are often attacked because they symbolize authority and governance, and targeting them can instill fear and disrupt societal order. Public transportation systems, with their crowded environments and accessibility, represent another vulnerable target that can cause mass casualties and chaos. Religious gatherings, which are gatherings of community and faith, are also seen as symbolic targets that can provoke strong emotional responses and further polarize groups within a society.

Thus, indicating that "none of these" has not been targeted implies a recognition of the extensive history of terrorist acts focused on each of these areas. This understanding reinforces the necessity of vigilance and security measures in protecting these potential targets from future attacks.