“两句三年得，一吟双泪流”是苦吟诗人（）的自述。A、孟效B、贾岛C、姚合D、卢仝

It is reported that 300 million people in China have eyesight trouble. More and more parents hope to save their children’s eyesight with medicine, or by correcting the ways that children read and sit. But in fact, one should start with the exercise on one’s feet. Here are three ways to save eyes:

First, don’t tie your shoes too closely. Try wearing comfortable and soft socks or walking without socks and shoes at home. While you are traveling, try wearing cloth shoes in order to improve blood circulation(循环).

Second, walking on tiptoes is good for one’s eyesight. It can fight against eyesight trouble. Numbers show that most of ballet(芭蕾) performers’ eyesight is better.

Third, rope skipping(跳绳) can also be good for one’s eyesight. While skipping rope, one has to move quickly, making both the brain and the eyes excited. It may also help make one grow taller.

Besides foot exercises, it is good to pull one’s ears. Pulling the ears 20 times quickly is also a great way. It can keep one’s eyes healthy.

小题1:What does the passage mainly talk about?

小题2:Why is most of the ballet performers’ eyesight good?

小题3:What shoes should you wear while traveling?

小题4:Is rope skipping good for eyesight?

小题5:Besides foot exercises, there is another way to save one’s eyes. What is it?

某同学根据平抛运动原理设计粗测玩具枪弹丸的发射速度v₀的实验方案，实验示意图如图所示，没有计时仪器．  

（1）实验中需要的测量器材是______；

（2）用玩具手枪发射弹丸时应注意______；

（3）实验中需要测量的量是______；

（4）计算公式V₀=______．

（5）用一张印有小方格的纸记录手枪弹丸的轨迹，小方格的边长L．若弹丸在平抛运动途中的几个位置如图中的a、b、c、d所示，则其平抛的初速度的计算式为V₀=______（用L、g表示），弹丸运动到b点的速度大小V_b=______（用L、g表示）．

银器的保养方法？

沉积厚度分析法——补偿与非补偿