关系数据库的三种基本关系运算是 (23) 。在关系代数运算中, (24) 运算结果的

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问题:

关系数据库的三种基本关系运算是 (23) 。在关系代数运算中, (24) 运算结果的关系模式与原关系模式相同。

A.选择、投影和连接

B.选择、删除和复制

C.创建、修改和合并

D.统计、连接和分类

考点:计算机软件水平考试初级程序员初级程序员上午试题
题型:单项选择题

Earthquakes can be very scary(吓人的). But you need to keep your mind stable (坚定的) in order to make sure you are safe. Be calm and try not to run here and there.

If you manage to come out of your house, go to an open space like a garden or a park where you will be a lot safer. If you live quite some floors above in your building, try to find a place near a bulky(坚固的) object such as a bed. Curl up (蜷缩) and sit on the floor and make sure you are not near a window, fireplace, gas stove and so on. Remember don’t use lifts or escalators.

Some people say you should stand on a doorway. That is not true. If the doorway jambs (侧壁) are weak, they might fall on you. Also if people want to pass through that door, you may stop them. Leave all doorways free.

Another important thing to keep in mind is that you mustn’t climb down the stairs during an Earthquake. If the tremors (震动) stop, after a few seconds, just climb down the stairs as quickly as you can and move out of the building, but don’t run.

Earthquakes usually destroy gas pipes and electrical wires. Turn off the main gas. And don’t light candles or lighters and create an even bigger disaster.

If you’re driving and feel a shake, stop your car at the side of the road and get out. Make sure you are not on a bridge. Bridges and overhead roads (高架路) have the biggest danger of falling.

小题1: The best title for the passage should be       .

A.Dos and Don’ts Before an Earthquake.

B.What to Do in Case of Earthquake

C.Tips for Earthquake Preventions

D.Tips for Children in Earthquake.小题2:When an earthquake suddenly happens, you should       .

a. remain standing near a window             b. turn off the main gas

c. stay in an open space                     d. stand on a doorway

e. keep off  overhead roads

A.a, b, c

B.c, d, e

C.b, c, e

D.b, d, e小题3: Which of the following is NOT true, when an earthquake suddenly happens?

A.We can’t use the lift.

B.Curling up may be very dangerous.

C.We must turn off the gas.

D.We must get out of the car when the earthquake comes小题4: It can be learned from the passage that     .

A.keeping calm in time of earthquake is very important.

B.measures should be taken to make buildings stronger.

C.Knowledge of first aid must be used in an earthquake.

D.lots of things must be done to survive an earthquake.

题型:单项选择题

符合21-三体综合征临床表现是的()

A.眼距窄

B.眼球凸出

C.通贯手

D.手指细长

E.皮肤白皙

题型:单项选择题

美国微软公司连连遭到起诉,因为它的经营过大,有垄断的嫌疑,而这起诉讼一旦成功,微软便可能被肢解。可见()

A.微软发展速度太快,这是美国政府不愿意看到的

B.微软为富不仁,引起同行的不满

C.美国是自由市场经济,不允许垄断存在

D.微软与美国政府没有搞好关系,微软的公关工作不利

题型:单项选择题

已知甲数列的算术平均数为100,标准差为20;乙数列的算术平均数为50,标准差为9。由此可以认为()。

A.甲数列算术平均数的代表性好于乙数列

B.乙数列算术平均数的代表性好于甲数列

C.两数列算术平均数的代表性相同

D.两数列算术平均数的代表性无法比较

题型:单项选择题

产后宫缩痛()

A.产后1~2日

B.产后第5日

C.产后10日

D.1周

E.2~3周

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