Write a question about the following article.

I went to my grandparent 's house for supper last night . It was my grandmother 's 92nd birthday . I was happy to find that the leaves had started to change and fall in her neighborhood , so I got some pictures .

Question:
why did the leaves start falling ?
Choose from: (I). because it was likely the fall season; (II). because it was the birthday of his family member; (III). because it was raining; (IV). None of the above choices .;