①已知 $M\left(-2，0\right)$ ， $N\left(2，0\right)$ ， $\left|PM\right|-\left|PN\right|=3$ ，则动点 $P$ 的轨迹是双曲线左边一支；

②已知椭圆 $\frac{x^2}{8-m}+\frac{y^2}{m-2}=1$ 的长轴在 $y$ 轴上，若焦距为 $4$ ，则实数 $m$ 的值是 $7$ ；

③抛物线 $y=2a{x}^2$ （ $a\ne 0$ ）的焦点坐标是 $\left(\frac{a}{2}，0\right)$ .

阅读材料，结合所学知识回答问题。

材料一：胡适说，北大是因为三个兔子而成名的，一是老兔子蔡元培；二是中兔子陈独秀，三是小兔子胡适本人（三人年有长幼，但都属兔）。

——洪向华主编《复兴之路》

材料二：它不仅是近代中国政治由旧民主主义革命转变为新民主主义革命的转折点，并且推动了近代新文化运动更加深入地健康发展，其具体体现是这次运动大大加速了来自俄国的新思潮在中国的传播，从而给新文化运动注入了新的、更为强大、更加科学的思想活力。

——摘自冯天瑜、何晓明、周积明《中华文化史》

材料三：***的成立，使中国革命的面貌焕然一新。***领导人民取得了新民主主义革命和社会主义革命的胜利。

——摘自人教版九年级《历史与社会》

材料四：每一场革命都有自身的传奇。***在开辟革命新道路历程中也不例外。“它不是一般意义上的‘行军’……它是一曲人类求生存的凯歌，是为避开蒋介石的魔爪而进行的一次生死攸关、征途漫漫的撤退，是一场危在旦夕、险象环生的战斗。”

——美哈里森·索尔兹伯里

①本质是商品

②具有使用价值和价值

③具有价值尺度职能

④制作成本低，携带方便

    I saw an accident on my way to the college three days ago.

    I was waiting for the bus at the but stop. When the bus came, I got on the bus and sat on the window side. The bus started to move. After about five minutes, the bus stopped to wait for the signal(信号灯). I looked outside and saw an old man crossing the road. There were not many people on the road. A boy was riding a motorbike very fast form my side. It seemed that he did not see the signal. When the boy took notice of the old man, he tried to slow down his motorbike but there was no time. He collided with the old man very badly. The old man was thrown far away The boy also fell down. His head hit the road but it was saved because of his helmet(头盔). Both of them lay in the pool of blood. Many people gathered(聚集) around them and gave their ideas. I got afraid because I saw the whole accident. Then a woman stopped and called the ambulance( 救护车 ). It came quickly and rushed them to hospital.

    The next day I read the newspaper. The old man died in the ambulance but the boy was saved in time. This was the most terrible accident I saw ever in my life.