高能量X射线设备，例如线性加速器，其主要原理是（）A、增加两极间的电压差 B、增高电

阅读理解。

     Internet is educational . Many  people  think  children  should be allowed to surf  the Internet as they

wish . In this way ,they can look through different subjects on  different  kinds  of  websites according to

their own interest . But in my opinion ,children should always be watched while surfing the internet .

     Many websites have information and pictures that children should  not  see . There  are  many  things

that children don't understand .All of  these  may have  some bad  influence on children 's  development .

Also , it is dangerous to let childern use chat rooms by  themselves .Many parents  tell  their children not

to talk to strangers on the street , so they should be careful of whom their children talk to on the internet,

too . What's more ,  sitting in the front of a computer  for a  long  time isn't good  for children's  eyes , so

parents should monitor(监视) the time that childen spend on the internet .

     In a word ,children should be kept away anything that could be bad for them . I strongly believe  that

it is necessary for paents to watch their children when they use internet .

1.Is the Internet educational all the time ?        

    ___________________________________

2. What do the parents tell children to do when they meet strangers on the street ?

   ___________________________________

3.Why shouldn't children sit in front of a computer for a long time ?

   ___________________________________

4.Who can help children stay away from the bad influence on the Internet ?

   ___________________________________

5. What does the writer want to tell us in the passage ?

    ________________________________      

下图为“探究凸透镜成像规律”的实验装置。

(1)点燃蜡烛后，调节凸透镜和光屏使它们的中心跟烛焰的中心大致在________上。

(2)为了找到像的准确位置，必须做好光屏的微调，即在一定范围内左右移动光屏，使光屏上的像由模糊到____，直至找到像最清晰的位置。

(3)如图，烛焰恰好在光屏上成倒立、等大、清晰的像，则该凸透镜的焦距是_   _cm。

(4)保持烛焰位置不动，把凸透镜从距烛焰一倍焦距处向烛焰移动2 cm，可以从________（填“光屏一侧”或“烛焰一侧”）通过凸透镜观察到烛焰正立、____ 的虚像，____就是利用了这一成像规律。

患者，女性，48岁，8月初由外地来京探亲，因"发热、头痛5天，神志不清2天"于9月18日入院，经查后确诊为流行性乙型脑炎。

提示病人出现中枢性呼吸衰竭的最可靠体征是（）

A.呼吸困难

B.呼吸急促

C.呼吸浅促

D.呼吸节律不整

E.出现"三凹征"

可作为肝移植时选择供肝依据的是（）

A.靛青率滞留率试验

B.ALP测定

C.利多卡因试验

D.血清铜测定

E.ALT测定

从莫斯科奥运会起，一支鸟类合唱团在福缅科指挥下，3年时间演出2000多场世界名曲和流行歌曲。这种鸟是：（）

A.黄雀

B.金翅雀

C.椋鸟

D.金丝雀