In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[Q]: Terrorism is a problem which has troubled the international community for more than _ decades.
[A]: three


[Q]: Sin has _ effects on every person's life.
[A]: two


[Q]: Upper canines are long and well-developed, and the molars have _ or four cusps.
[A]:
three