完形填空

     When I was 13 years old, a boy gave me an important gift. It was a   1  It was the early autumn of my first year at a junior high school and my old school was far away.  2   , no one knew who I was. I was very lonely and afraid to make friends with   3  Every time I heard the other students talking and laughing, I  4  my heart break. I couldn't talk to anyone about my problem, and I didn't want my parents to   5  me. Then one day, my classmates talked happily with their friends, but i sat my desk   6   as usual. At that moment, a boy entered the classroom. I didn't know who he was. He passed me and then turned back. He   7  me and without a word, just smiled.

     Suddenly I felt the touch of something bright and friendly. It   8  me feel happy, lively and warm. That smile changed my life. I started to talk with the other students and made friends. Day by day, I became closer to everyone in my class. The boy with the lucky smile   9  my best friend now.

     I believe that the world is what you think it is. If you think you are lonely, you might always be alone. So smile at the world and it will   10

已知函数$f\left(x\right)=\frac{x}{x^2+1}$，关于f（x）的性质，有以下四个推断：

①f（x）的定义域是（﹣∞，+∞）；       ②f（x）的值域是$\frac{1}{2},\frac{1}{2}$；

③f（x）是奇函数；                   ④f（x）是区间（0，2）上的增函数．

其中推断正确的个数是（　　）