Answer:
Correct answer is A. clashes between groups with different religious or political beliefs.
Step-by-step explanation:
Option A is correct, as with the rise of Islamic fundamentalism at the beginning of 21st Century the conflict arose, especially in the area of Middle East.
B is not correct as there were no such conflicts at the time.
C is not correct as UN has a mutual role to preserve peace in the world, and internal conflicts are not usual in it.
D is not correct as leaders were addressing terrorism in the same manner.