阅读下面的短文，从每题所给的A、B、C和D四个选项中，选出可以填入空白处的最佳选项
   It is very important to stay healthy. I have a neighbor. She is an old lady. She can do all the housework,  1 newspapers, watch TV and search on the Internet to learn something new. I often see 2 do Taijiquan in the morning and dance in the evening. She looks young and beautiful 3 she is over seventy. Last week a reporter from a magazine interviewed her and asked 4she kept so young and healthy. She replied with a smile:
   I have a secret of staying young and healthy. It is quite 5. Keep your mind active, take an interest in the world 6 you., and learn at least one new thing every day. Try to do different kinds of housework and do sports as  7 as you can. Don’t think you are too old to go back to8. I know a man who entered a medical college when he was 70 years old. He studied there for 6 years and now he is a doctor. Another man went to a tennis school at the age of 72 and now he is good at 9 tennis. Some people may say staying young is easy only for those who live in the future. In fact, no matter how old you are, you can make it.
   Please tell the story to your family. It would be a good start to 10 the lady’s example. I hope all people will stay young and healthy.

（2015•抚顺）生活与化学息息相关，请用学过的化学知识回答下列问题．

（1）合理膳食有益健康，牛肉富含的营养素是 ____．

（2）熄灭蚊香时，通常把燃着的一端剪断，灭火原理是 ____．

（3）净化水时，水中异味用 ____（填物质名称）除掉；生活中通常用 ____方法降低水的硬度．

（4）乙醇汽油是汽车燃料之一．乙醇属于 ____（填“可再生”或“不可再生”）能源；使用乙醇汽油可以减少一些有害物质的排放，如　 ____（填一种即可）．