已知定义在R上的函数f（x）满足：f（x+1）=$\frac{1}{f\left(x\right)}$，当x∈（0，1时，f（x）=2^x，则f（log₂9）等于____ 

读图，完成下列要求．

若集合$A=\{-2,-1,0,1,2\},B=\{1,0,2,3\}$ ，则$A\cap B=$（    ）

生铁和钢是碳含量不同的铁合金，是____ （填“合成”或“金属”）材料．工业上，冶炼生铁的原理是一氧化碳与赤铁矿石反应，利用了一氧化碳化学性质的还原性，反应的方程式为____ ．得到生铁很容易生锈，铁生锈实际上是铁与____ 发生化学反应的过程．为了使生铁不生锈通常在铁制品的表面采取的措施是____ ．

    If you are writing or studying, it makes much difference where the light comes from. People use  1and pens every day. They have to be very careful about the way of the light because the light shines on their work.
    Every  2 gets its light either from daylight  3 the window  4 from the lamps or electricity,  5no matter what kind of light it is, the way it shines towards our books or work is very important to the eyes.
    Take a book and sit with your  6 toward the window, and try to read. Your shadow(影子) falls all over the page and makes it  7 for your eyes as if you were in a  8 room.
    Now turn around and face the window. The page is  9 shadow again, while the bright light is in your eyes.
    Try sitting with your  10side toward the window. This is very good for  11 , but if you were writing, the shadow  12 fall across the page and bother you  13 .
    There is another way – sit  14 your left side to the window. Now everything is perfect for writing as well.
    Whatever kind of light is in the room, the rule about the right way to sit is  15 the same.