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: 数据库系统虽然减少了数据冗余,但不能避免一切冗余,选项A正确,选项B错误;数据的不一致性是指对数据的存取方式,而不是数据类型一致,选项C错误:不管有多少数据,数据库系统和文件系统都可以管理,选项D错误。

阅读理解

阅读理解

     Some plants get so hungry they eat flies, and even small frogs. What's more amazing is that these plants occur naturally (in special environments) in every state. In fact, they're found on every continent except

Antarctica.

     You've probably seen a Venus' flytrap -- a small plant, which grows 6 to 8 inches tall in a container. At the end of its stalks (茎) are leaves that act like traps (陷阱). Inside each trap is a lining of tiny hairs. When an insect lands on them, the traps suddenly shut. Over the course of a week or so, the plant feeds on its

catch.

     The Venus' flytrap is just one of more than 500 species of meat-eating plants, says Barry Meyers-Rice, the editor of the International Carnivorous Plant Society's Newsletter. He states although you might have

read some science-fiction stories, no meat-eating plant does any danger to humans.

Barry says a plant is meat-eating, only if it does all four of the following: "attract, kill, digest, and absorb"

some form of insects. Meat-eating plants look and act like other green plants -- well, most of the time.

All green plants make sugar to produce food. What makes meat-eating plants different is their special

leaves, which need insects for one reason: nitrogen (氮). Nitrogen is a nutrient that they can't obtain any

other way. Why?

     Almost all green plants on our planet get nitrogen from the soil. Meat-eating plants can't. They live in

places where nutrients are hard to get from the soil because of its acidity. So they've come to rely on

getting nitrogen from insects and small animals. In fact, nutrient-rich soft is poisonous to meat-eating plants. Never fertilize (施肥) them! But don't worry, either, if they never seem to catch any insects. They can

survive, but they'll grow very slowly.

1. According to the passage, a Venus' flytrap ______.

A. is a small plant which grows in a container

B. is a kind of plant which gets hungry easily

C. can trap and feed on some form of insects

D. can only grow 6-8 inches tall

2. From the passage, we can infer that ______.

A. meat-eating plants are found nowhere else except Antarctica

B. all green plants get nitrogen from the soil

C. meat-eating plants endanger humans in science-fiction stories

D. the nutrient-poor soil is beneficial to meat-eating plants

3. Meat-eating plants grow very slowly, ______.

A. so you'd better fertilize them

B. probably because the supply of nitrogen is cut off

C. simply because they can't absorb nitrogen from the soil

D. and then they will die slowly

4. Which of the following is true?

A. Meat-eating plants look and act like other green plants.

B. It's hard to get nutrients in the soil when acidity is high.

C. The Venus' flytrap eats flies to get nutrient from them.

D. Green plants make sugar at night.

单项选择题