Escaping (逃) from a fire is a serious matter. Knowing what to do during a fire can save a life. It is important to know the ways you can use and show them to everyone in the family, for example, you can use stairways, roofs and fire escapes, but no lifts.
    From the lower floors of buildings, to escape through windows is possible. Learn the best way of leaving by a window with the least chance of serious injury.
    The second floor window is usually not very high from the ground. An average (平均) person, hanging from the window by the fingertips will have a drop of about six feet to the ground--about the height of an average man. Of course, it is safer to jump a short way than to stay in a burning building.
    Windows are also useful while you are waiting for help. Be sure to keep the door closed, before opening the window. Otherwise, smoke and fire may be drawn into the room. Keep your head low next to the window to be sure you get fresh air.
On the second or third floor, the best windows to escape from are those which open onto a roof (屋顶) . From the roof a person can drop to the ground more safely.

先化简再求值：$\left(\frac{a-2}{a^2+2a}-\frac{a-1}{a^2+4a+4}\right)÷\frac{a-4}{a+2}$，其中a满足$a^2$+2a-1=0．

材料一：抗日战争胜利后，国民党阴谋发动内战，全国人民渴望和平和民主。面对这种形式，蒋介石的谋士陶希圣说：“利用谈判拖一拖也好。共产党拒绝谈判，我们更有文章好做。”1945年8月，蒋介石在短短的十天之内一连三次电邀***“共同商讨国家大计”。

材料二：***《七律•人民解放军占领南京》

钟山风雨起苍黄，百万雄师过大江。虎踞龙盘今胜昔，天翻地覆慨而慷。宜将剩勇追穷寇，不可沽名学霸王。天若有情天亦老，人间正道是沧桑。