问题 单项选择题

下述关于数据库系统的叙述中正确的是

A.数据库系统减少了数据冗余

B.数据库系统避免了一切冗余

C.数据库系统中数据的一致性是指数据类型一致

D.数据库系统比文件系统能管理更多的数据

答案

参考答案:A

解析: 数据库是一个通用化的、综合性的数据集合,它可以为各种用户所共享,具有最小的冗余度和较高的数据与程序的独立性,而且能并发地为多个应用服务,同时具有安全性和完整性。即数据库系统减少了数据冗余,但不能避免一切冗余。所以选项A正确,选项B错误。 在数据库管理阶段中,数据是结构化的,面向系统,数据冗余度小,从而节省了数据的存储空间,也减少了对数据的存取时间,提高了访问效率,避免了数据的不一致性。数据的不一致性,是指对数据的存取方式,选项C错误。 数据库系统比文件系统能管理更多的数据,并非数据库系统的特点,选项D错误。 本题正确答案是A。

多项选择题
阅读理解

阅读理解。

     Once considered a fringe(非主流的)food by the U.S. culinary mainstream, sweet potatoes are

fast becoming popular everywhere from fast food chains to expensive restaurants and the White

House table.

    Three years ago, the "Wall Street Journal" wrote in a front page article that except for their use in

a Thanksgiving dish, sweet potatoes were a wholly uninteresting food. Yet over the past two years,

the number of restaurants offering a sweet potato-based side dish has increased 40 percent. Food

giant ConAgra just spent $155 million to open the world's first plant devoted entirely to frozen sweet

potato products, and U.S. farmers are planning to harvest a record-setting 2 billion pound crop.

    "It's not something we believe is a fashion,"said Andy Johnston of ConAgra Foods Lamb Weston.

    According to research conducted by ConAgra, 30 percent of sweet potato eaters report consuming

the vegetable several times per month. Only 12 percent eat them only during the Thanksgiving and

winter holiday season.

    Analysts attribute the sweet potato's growing popularity in large part is due to sweet potato fries,

which account for the majority of the vegetable's presence in U.S. restaurants. In fact, Google searches

for "sweet potato fries" increased 40 percent over the past year.

    Sweet potatoes have also become popular among more conscious eaters, however, in part because

they are high in vitamins and have a low glycemic (血糖的) index in spite of their sweetness. Both

Weight Watchers and the South Beach Diet have recommended sweet potatoes, roasted in a little oil

rather than fried, and doctors are recommending them for diabetics.

   "Within the diabetic community, it's become pretty common knowledge that sweet potatoes are good

for you, so there's a great appeal because so many people have diabetes now,"said Chef Michel Nischan, who helps host a TV show for people with diabetes.

1. From this reading passage we infer that ConAgra __________.

A. is one of the biggest food-making companies in the US

B. is one of the richest food-selling companies in the US

C. has asked American farmers to produce more sweet potatoes this year

D. has produced large quantities of sweet potato-based side dishes

2. According to the ConAgra research, the number of people who often eat sweet potatoes ________.

A. is increasing very quickly          

B. is not very big

C. is falling a little bit                

D. has nearly doubled

3. Which of the following may NOT encourage the sweet potato's popularity?

A. US restaurants recommend sweet potatoes to their customers as a vegetable.

B. Google searches show more and more people are becoming interested in sweet potatoes.

C. Sweet potatoes are rich in vitamins and low in glycemic index.

D. Sweet potatoes taste very sweet.

4. Chef Michel Nischan will certainly agree that _____________.

A. sweet potatoes should be fried

B. sweet potatoes should be roasted

C. sweet potatoes are good for diabetics

D. sweet potatoes can be made into many good dishes