设关系及和S的元数分别是r和s，则它们的笛卡儿积是多少个元组的集合A．r+s B．r

关于脊髓灰质炎病毒，哪项是错误的

A．主要经粪-口途径传播

B．分为Ⅰ、Ⅱ、Ⅲ3个型别

C．各型病毒之间有共同抗原

D．主要感染脊髓运动神经细胞

E．口服减毒活疫苗可进行预防

排泄的主要器官是

A．肝
B．肾
C．胆囊
D．小肠
E．胰脏

阅读理解。

     You are standing in the kitchen and a voice says, "Add a little more salt to that soup." Yes, it's always

nice to have someone help you when you're cooking. But this voice is not from a man. You are alone!

Then where does it come from? Is it from a ghost? No, this isn't a ghost kitchen-it's the kitchen of the

future.

     Scientists are working to improve everything in the kitchen, from fridges to tables, and even the ways

we cook. They are making a system. It will help a person cook a meal. You don't need cookbooks. You

can hear how to cook food.

     The fridge of the smart kitchen has a scanner. It looks at the foods in the fridge. It will order more milk

from the store when your milk has gone bad or there is no more in the fridge. The gloves will test the

temperature of everything they touch and say, "Need to cook longer" or "Hot and ready to eat". If you

leave them on the stove by mistake, they'll say, "Fire!" Even the knives and spoons will speak. For

example, if your food is bad, the knives and spoons will tell you not to eat it.

     The future kitchen may look wonderful, but it's not cheap. The multimedia fridge costs about 8,000

dollars. So even though high-tech kitchens are no longer a dream, not everyone can afford one.

1. In the kitchen of the future, there is a ______ helping you.

A. system        

B. man        

C. ghost        

D. servant

2. In the future, you can cook by ______. 

A. reading        

B. hearing    

C. learning      

D. looking

3. The fridge of the smart kitchen has a scanner and it can ______. 

A. help you do everything          

B. clean the fridge when it's dirty

C. give you a warning when there's something wrong    

D. talk with you

4. From the passage we know that ______.

A. everybody can buy such a fridge    

B.not everybody can buy such a fridge        

C. nobody can buy such a fridge      

D. most people can buy such a fridge

互联网的第一次快速发展出现在（）

A.二十世纪九十年代初期

B.二次大战中

C.二十世纪六十年代末期

D.二十世纪八十年代中期

在路基内埋设电缆时，必须遵守《铁路路基大修维修规则》的规定，并保证路基及其排水、防护和加固设备的稳固和完好状态。（）