In answering a question like this, it is best to look at your text and/or your lecture notes. This question can be interpreted and answered in different ways and your instructor may be looking for specific answers from the text or from what has been discussed in class. That said, let us look at one way in which to answer this question.
The overall answer to this question is quite clear. World War II “disrupted” the multipolar world because it led to the creation of two superpowers and the destruction or severe weakening of many countries that had been seen as great powers before the war. Before the war, there were many powers that were thought to be important. These included Great Britain, France, Germany, Italy, the United States, Japan, and the Soviet Union. After the war, the US and the Soviet Union were superpowers and no other country was a truly important power. What is less clear is how to pick three events that “led to this situation.”
Clearly, World War II is one event that “led to this situation.” WWII destroyed or severely reduced the military and economic capacities of many of the former great powers. Germany and Japan were devastated by bombing and were defanged in military terms by the Allies after the war ended. Germany was also torn apart, further reducing its ability to be a major player in world politics. Like Germany and Japan, France was physically harmed. More importantly, perhaps, it lost tremendous prestige in the world because it had been defeated so easily by Germany. Great Britain was economically devastated by the need to pay for the war, putting it greatly in the debt of the United States and taking away its ability to have a major military force. Thus, WWII clearly contributed to the disruption of multipolarity.
We can also say that the industrialization of warfare helped to disrupt the multipolar world. In the post-WWII world, it became clear that military strength was connected to economic strength. Whichever country could marshal the most resources was likely to win any major war. This meant that countries could only be real powers if they had huge industrial bases. Only the US and the USSR could make this claim.
Finally, we can say that the Cold War was an “event” that “led to this situation.” The Cold War forced countries to take sides in a bipolar way. Before WWII, there had been no ideologies around which various countries could coalesce. With the coming of the Cold War, it became natural for countries to split up into two blocs. This, too, reduced the level of polarity in the world.
World War II, and the Cold War after it, put an end (at least so far) to multipolarity in the world. WWII devastated many of the former “great powers” and the Cold War caused a move towards bipolarity. We have yet to return to a multipolar world order.