问题 单项选择题

数据库设计中,用E—R图来描述信息结构但不涉及信息在计算机中的表示,它属于数据库设计的

A.需求分析阶段

B.逻辑设计阶段

C.概念设计阶段

D.物理设计阶段

答案

参考答案:B

解析: 用E-R图来描述信息结构属于数据库设计的逻辑设计阶段。

单项选择题
阅读理解

CANBERRA(Reuters)—Australia’s kangaroos are genetically similar to humans and may have first evolved in China, Australian researchers said Tuesday.

Scientists said they had for the first time mapped the genetic code of the Australian marsupials(有袋类)and found much of it was similar to the genome for humans, the government backed Center of Excellence for Kangaroo Genomics said.

“There are a few differences, we have a few more of this, a few less of that, but they are the same genes and a lot of them are in the same order,”center Director Jenny Graves told reporters in Melbourne.

“We thought they’d be completely scrambled, but they’re not. There is great chunks of the human genome which is sitting right there in the kangaroo genome,” Graves said, according to AAP.

Humans and knagaroos last shared an ancestor at least 150 million years ago, the researchers found, while mice and humans separated and went in different ways from one another only 70 million years ago.

Kangaroos first evolved in China, but migrated across the America to Australia and Antarctica, they said.

“Kangaroos are hugely informative about what we were like 150 million years ago,” Graves said.

68.Where does the kangaroo first develop according the scientists?

A.In China.    B.In America. C.In Australia.       D.In Antarctica.

69.What does the passage mainly tell us?

A.How the Kangaroo first evolved.      B.Kangaroo’ genetic code have been mapped.

C.Kangaroos’genes are close to humans’.     D.Scientists did much research into Kangaroos.

70.What does the underlined word “scrambled” probably mean in the fourth paragraph?

A.Funny. B.Wrong.       C.Curious.      D.Right.