若等差数列{an}的前n项和为Sn，且a2+a10+a12为一确定的常数，则下列

阅读理解。

     Many of us don't pay much attention to the importance of eye care. It is said that if you take care of

your body, then you can surely be healthy. That is why our eyes should be given a lot of care. Natural eye

care should be put in a number one place.

     There are several causes leading to poor eyesight like not enough food, genes (基因) and aging (老化).

Televisions, computers and reading are also the causes of having poor eyesight. If you happen to work in

front of the computer, it is best to take a break every once in a while. Something dirty can cause redness and

they will make you feel uncomfortable. It is bad for your eyes, too. If this happens, the best way is to clean

your eyes by using cold water. You must also try your best to protect your eyes from harmful things. For

example, sunglasses are not just for fashion but they can also serve as a great way to protect your eyesight

form UV rays.

     Eating healthy foods will do good to your eyesight. Remember that vitamins A, C and E are good for eyes.

Try to eat food groups that have these vitamins. And you should do eye exercises because exercise protects

your eyesight, too. If a person exercises regularly (定期地) and eats the right kind of food, his eyes will stay

in good condition for a long time.

     All above are natural ways of eye care that help us keep healthy eyes. Being happy all the time can be

helpful to a person's eyesight, too. In a world, eye care is very important, no matter how old a person is.

1. _______ is the most important way to protect our eyes.

A. Natural eye care

B. Taking medicine

C. Seeing the doctor

D. Being happy all the time

2. All the following causes can lead to bad eyesight except _______.

A. age

B. height

C. reading

D. computers

3. What should you do if you have to work in front of the computer?

A. Eat healthy foods.

B. Clean the eye by using cold water.

C. Wear a pair of sunglasses.

D. Have a rest after working for a while.

4. What do the underlined words "UV rays" mean?

A. 沙尘

B. 闪电

C. 紫外线

D. 超声波

5. Which is the best title of the passage?

A. Ways of Eye Care

B. Ways of Eye Exercises

C. Ways of Being Happy

D. Ways of Being Healthy

一引水式水电站通过环境影响评价并被批复后，历经3年建成，为日调节电站，功能是防洪、发电、灌溉，并兼有渔业功能。坝高30m，死库容约1.8亿m³，最高洪水位320m，最低死水位160m。坝址上游有一中型城市，水库回水段上游即是城市饮用水取水口，但未划分保护区。坝址下游有较多的农田，群众反映灌溉用水不足且产量有所下降。现已投入试运行，竣工验收调查由当地一家环评单位承担，调查发现有洄游性鱼类，但当时建设时未发现有洄游性鱼类，所以没有建过鱼设施。由于库区移民安置采取的是就近后靠的方式，陡坡开垦农田明显，而且有部分移民返迁。坝址下游减脱水段有一个弃渣场。现在库区鸟类较多，其中有国 * * 护鸟类约3种。

现状主要环境问题有哪些

施工投标工程量清单报价的程序中，询价的渠道主要包括( )等。

A．通过互联网查询

B．向生产厂商的代理人或从事该项业务的经纪人了解

C．向经营该项产品的销售商了解

D．间接与生产厂商联系

E．自行进行市场调查或信函询价

观光农业按经营模式分类有哪些？

（）保卫国家、维护国家安定，空军保卫领空、歼敌，警察、海关行使国家职责。

A、军事航空

B、民用航空

C、航空制造业

D、航空设计