题目

How to Improve Eyesight Naturally     Eyes are important for everybody．You must take care and try everything in your hand to keep them in good condition．Here are some of the tips to improve your eyesight naturally．         1   Strain is known to be a factor in many health conditions and eyestrain is no exception．Try meditation，yoga or other methods of stress relief to improve your vision and overall health．Try palming．Sit upright in a comfortable chair．   2     Cup your hands so that there is no pressure on your eyes．Let your fingers rest across学习化学可以使你变得更聪明，可以帮你解释生活中的许多问题．（1）我国古代用墨写的字虽年深日久仍不变色，其原因是 ________；（2）潜水艇中需要配备氧气再生装置，利用的是过氧化钠（Na2O2）与二氧化碳反应生成碳酸钠和氧气，该反应的化学方为 ________．（3）要使煤炉中煤燃烧得更旺，可以将煤粉碎，也可以鼓入空气，请你用学过的知识加以解释 ________．（4）在商店购买灯泡时，灯丝支架上附有少量的红色物质--红磷．其作用是：________．