在关系数据模型中，二维表的行称为元组，二维表的列称为______。

患者，男性，18岁。转移性右下腹痛6小时，伴恶心呕吐，右下腹有固定而明显的压痛点，诊断为急性阑尾炎。采用非手术治疗。不必要的护理措施是（）。

A.流质饮食

B.静脉输液

C.胃肠减压

D.使用抗生素

E.禁用止痛剂

表皮黑素单位内角质形成细胞与黑素细胞的比例为

A．20：1

B．30：7

C．15：1

D．2：1

E．36：1

Should we try to contact and make friends with other beings in the universe? Certainly not，says British physicist Stephen Hawking．

“If aliens（creatures from other planets）ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans,’’ said the 68-year-old disabled scientist in a new Discovery documentary (纪实性电视节目) on April 25．

The program pictures an imagined universe where other life forms in huge spaceships hunt for resources after using up all those on their home planets．

“Such advanced aliens would perhaps become nomads(游牧民)，looking to conquer and colonize whatever planets they can reach，”warned Hawking．

On the probability of other life forms existing, he says, “To my mathematical brain, the numbers alone make thinking about aliens perfectly reasonable.”

Hawking’s concerns have frightened some people and been met with disagreement from other researchers．Paul Davies, author of the book Renewing Our Search for Alien Intelligence，thinks Hawking’s reasoning is wrong.

He argues that since Earth is about 4.5 billion years old，if intel1igent life is likely , communities of other beings may have been there for a very long time．

“If resources are the factor, then at least one group of aliens would surely have visited Earth as a destination mil1ions of years ago．

Even if other life forms do come to Earth in the near future, Davies believes comparisons with are wide of the mark(离谱的).

68. What is the article mainly about? 

A. Other life forms coming to our planet．

B. Scientific evidence of other life forms．

C. Earth as the only place where human beings can survive．

D. Hawking’s belief that other life forms may exist in the universe．

69. Which of the following ideas is opposed to Hawking’s view?

A. Other life forms exist in the universe．

B. 0ther life forms may be more intelligent than human beings．

C. We should try to contact other 1ife forms from other planets．

D. Other life forms may exist in more than one part of the universe．

70. Paul Davies didn’t agree with Stephen Hawking ,believing that ________．

A. the universe is running out of resources

B. humans are the best creatures in the universe.

C. it is a good idea to avoid meeting with other life forms   

D. Davies doesn’t think it proper to compare aliens with Columbus

71. Hawking referred to Christopher Columbus as an example to ____．

A. inspire interest in the universe      

B. draw attention to other planets in the universe

C. warn people to watch out for other life forms

D. urge further exploration of the universe~

过滤废水后形成的滤渣不能用反洗方法来清除。

甲注册会计师对A公司2009年的50000张销售发票的赊销批准情况进行控制测试。甲注册会计师根据以前的经验估计大约有2.5%的发票缺乏批准手续程序，在对一个由200张销售发票组成的样本进行检验后发现其中有7张发票缺乏批准手续，甲注册会计师评估的偏差率上限定为8%，甲注册会计师应当将抽样风险允许限度确定为( )。

A．5.5%

B．4.5%

C．3.5%

D．1%