Answer: I'm sure that the answer is A - Nations became more isolated and refused to form alliances.
Explanation: Because the question is, "How did the trend toward nationalism, militarism, and imperialism lead to the start of World War I?" Honestly, the answer that sounds the most correct is A but I'm not that sure. The other answers don't seem that right.
Another Explanation: The World War I was caused by (alliances, imperialism, militarism, nationalism) You can even search it up and it'll show...I'm sure that this is the answer because will I just gave you the explanations. I'm really trying to help here and I'm sure that this is the correct answer.
3rd Explanation: I'm sure that this is the correct answer and all but you can choose if you want to think that its right, if its wrong I'm sorry.
I really hope this helps +