① 要使像能够成在光屏的中央，应将光屏向____（选填“上”或“下”）；

② 实验过程中，当烛焰距凸透镜15cm时，移动光屏至某一位置，在光屏上得到一等大清晰的像；接着使烛焰向左移动5cm，此时应该将光屏向____移到某一位置（选“左”或“右”），才能在屏上得到倒立、清晰的实像；

③ 当烛焰距凸透镜10cm时，光屏上得到了一个清晰的实像，应用这一规律可以制成____（选填“照相机”或“投影仪”）。

下列命题中，正确命题的个数为（   ）
（1）三点确定一个圆  （2）平分弦的直径垂直于这条弦
（3）等弧对等弦      （4）直径是圆的对称轴

   There are many ways for us to reduce (减少) waste. For example, we can reuse paper and plastic bags. We can also recycle newspapers, glass, and cans (易拉罐)  1new things. Here are some useful 2 to reduce waste.
   Write on both sides of paper
   Many people write on only one side of their paper. Why not try using both sides? Some students only use half the pages of their 3 before getting new ones. Try to use up all the paper. People often give cards on birthdays or festivals. How about trying to 4 e-cards (电子贺卡) instead?
   Don’t throw away your old batteries (电池)
   Maybe you do not know that old batteries make the soil 5. This is because they have poisonous (有毒的) parts in 6. So, don’t throw away batteries. 7 them together. Try to use rechargeable (充电的) batteries for your games and CD players.
Give 8 all your unwanted clothes
   There are many poor families in China. You may ask your mother to keep your unwanted clothes. Then you can pass them on to those poor children. You will feel happy that you are 9 someone else. Also, you can see  10 your friends or relatives (亲戚) want them before throwing them away.