在数据库的概念结构设计中，常用的描述工具是______。

Karen,grown up in a very traditional family in the western United States,maintained high moral(道德的) standards throughout her youth.In 1984,at the age of 23,she married Bill.They were blessed with two children,a boy and a girl.

By 1991 their love had deepened,and they were happy.Later that year,Bill developed a white spot on his tongue.He visited a doctor.

One day shortly after that,Bill called Karen to sit beside him.He said with tears in his eyes that he loved her and wanted to live forever with her.The doctor suspected that he had been infected with HIV,the virus that leads to AIDS.

The family was tested,Bill and Karen’s results were positive.Bill had become infected before he met Karen;then he passed the virus on to Karen.The children’s results were negative.Within three years,Bill was dead.“I don’t know how to express what it is like to watch the once handsome man you love and intend to live with forever dying slowly.I cried many nights.He died three months short of ten years of our marriage,”says Karen.Though a doctor told Karen that she would soon follow her husband into death,she is still alive.The infection has progressed to the early stages of AIDS.

Karen is but one of about 30 million people now living with HIV/AIDS,a figure larger than the combined populations of Australia,Ireland and Paraguay.According to one UN report,Africa has 21 million of these victims.By the turn of the century that number could reach   40  million and the disease will bring on the greatest disaster in human history.Of the world’s sexually active adults aged 15 to 49,1 in 100 has already been infected with HIV.Of these,only 1 in 10 realizes that he or she is infected.In some parts of Africa,25 percent of the adults are infected.

Since the beginning of the spread of AIDS in 1981,about 11.7 million people have died of it.It is roughly calculated that in 1997 alone,about 2.3 million people died of it.Nevertheless,there are fresh reasons for optimism in the battle against AIDS.During the past few years,there has been a drop in new AIDS cases in wealthy nations.In addition,promising drugs hold out hope of better health and longer life.

小题1:By telling the story of Karen,the author intends to______.

A．warn people against high risk behaviors

B．stress the importance of medical tests

C．express sympathy for AIDS victims

D．show the consequences of AIDS小题2:The underlined part in Paragraph 1 most probably means “_______”.

A．were lucky in having

B．were asked to adopt

C．regretted having

D．gave birth to小题3:Bill was suspected of being infected with HIV after______.

A．he got married to Karen

B．the family members were tested

C．Karen persuaded him to see the doctor

D．he found something wrong with his tongue小题4:It can be concluded from the passage that______.

A．promising drugs will soon stop AIDS

B．the spread of AIDS could be controlled

C．it is hopeless to win the battle against AIDS

D．the death rate of AIDS patients has been reduced

在空气中下列哪种物质以气态存在（）。

A.乙醇

B.铅

C.铬

D.一氧化碳

E.香烟

中国和日本都是1980年《联合国国际货物销售合同公约》的缔约国，根据公约的有关规定，下列表述中正确的是哪一项

A．营业地在中国的某公司和营业地在日本的某公司之间签订的货物买卖合同中约定适用日本法是有效的

B．营业地在中国和日本的两公司订立的专利许可协议应当适用公约

C．营业地在中国和日本的两公司订立的货物买卖合同中选择了FOB术语，则表明公约的适用被排除

D．营业地在中国和日本的两公司订立的货物买卖合同是否有效，可以适用公约来确定

机车车辆用折角塞门的标记示例：折角塞门DN32TB/T1133-1999，组装好后，车辆用的折角塞门须以600Kpa的压缩空气进行气密性试验，机车用的折角塞门须以（）进行试验，不得泄露。

A.600Kpa

B.700Kpa

C.800Kpa

D.900Kpa

初产妇，孕34周，重度子痫前期。经治疗2天，病情无改善，需终止妊娠。下述哪项检查是不必要的（）

A.HPL测定

B.E₃测定

C.NST检查

D.宫颈黏液检查

E.羊水US值测定