阅读下面短文，从短文后各题所给的A、B、C、D四个选项中选出能填入空白处的最佳选项。
I used to live in my own room alone. But one day it all changed when my brother Jack asked to share my 1. At first, my parents said “no” to him, but at last my mother agreed. I cried and asked my parents not to do this, 2 it didn't work.
As soon as Jack entered (进来) my room, it began to become 3. To my anger, he often left his unwashed clothes and toys everywhere!
One evening, I was doing some 4 on my computer while Jack was listening to music.5, I left my seat to get some water. A big surprise was waiting for me when I 6. He was using my computer to play games. I had forgotten to save (保存) the homework. Sadly, he had closed my program 7 saving it—all I had done had disappeared (消失)! I 8 him. He cried a lot as my mother came and beat him. My mother also asked him to leave my room at once.
Then I did my homework 9. At 10:00 pm. I finished it. When I was going to turn off the 10, I saw the photo of my 11 that he had put on my table. I looked at his lovely face and remembered how 12 he was when my mom beat him. I really felt 13. I went to see what he was doing. I found he was 14 in my parents' bed. I kissed his face. He woke up, got up and said, “I'm sorry. I won't bring you any more trouble.”
I was so moved (感动的) and said, “From now on, my room is not only mine. It is 15!” That very night, Jack and I shared not only the room, but the bed.
中，自变量x的取值范围是_________
