如图是我国四条重要的山脉位置示意图，图中既是我国地势第二、三级阶梯分界线，又是我国季风区与非季风区分界线的山脉是（　　）

在同一平面内，三条直线的交点个数不能是（　　）

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    Tyler was a troublesome student. He sat in the back row. Every time I called him to answer questions, he'd reply with a flip（轻率的）answer. If he got it wrong, he would get very angry.
    Usually kids could sit quietly in class. However, Tyler was just loud. One day, Tyler was talking while I was teaching. I said to him, “Tyler, why not join in our discussion instead of having one of your own?” He got up from his chair, pushed it over, and shouted something I can't remember. I sent him to the office and he received a week's out-of-school punishment.
    The week was a wonderful time for me, but when it came to an end, I began to feel worried. So I came up with a plan. On the day of his return, I told him I wanted to start over with him. If he felt like he was going to lose control in class, he could step outside the door for a moment.
    From then on, Tyler was a changed student in my classroom. In fact he was a smart child and he even stopped a fight between two students one day. And he never used the privilege（特权）to leave the class for a moment. I believe that just letting him decide for himself made all the difference.
    When the year was over, he wrote me a thank-you note about how good the year had been for him. I still have it today and find it very moving to reread when I get stressed about teaching.