题目

阅读填空 Vanilla is my best friend. She is a lovely girl with two beautiful big eyes. But she always hides them behind a pair of glasses. One day, though, I nearly ended our friendship. I remember that day clearly. We were sitting in the classroom. The teacher was giving us our results of a Chinese test. I had done badly. I felt so sad that I wouldn’t talk to anyone. At lunchtime, I even stayed in the classroom alone. Suddenly, I heard a voice. It was Vanilla. “You look very unhappy,” she said, “What’s wrong?” I looked up at her, but said nothing. I knew Vanilla had got 用长为4cm，5cm，6cm的三条线段围成三角形的事件，是______事件．