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问题 选择题

若三条线段中a=3，b=5，c为奇数，那么由a、b、c为边组成的三角形共有（　　）

A．1个

B．3个

C．无数多个

D．无法确定

答案

根据三角形的三边关系，得

5-3＜c＜5+3，2＜c＜8．

又c是奇数，则c=3或5或7．

故选B．

单项选择题 案例分析题

Wise buying is a positive way in which you can make your money go further. The （）you go about purchasing an article or a service can actually （）you money or can add （）the cost.

Take the （）example of a hairdryer. If you are buying a hairdryer, you might （）that you are making the （）buy if you choose one （）look you like and which is also the cheapest （）price. But when you get it home you may find that it （）twice as long as a more expensive （）to dry your hair. The cost of the electricity plus the cost of your time could well （）your hairdryer the most expensive one of all.

So what principles should you （）when you go out shopping?

If you （）your home, your car or any valuable （）in excellent condition, you’ll be saving money in the long （）

Before you buy a new （）,talk to someone who owns one. If you can, use it or borrow it to check it suits your particular （）

Before you buy an expensive （）,or a service, do check the price and （）is on offer. If possible, choose （）three items or three estimates.

请在第（）处填上正确答案。

A.convince

B.accept

C.examine

D.think
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单项选择题

石油中芳烃和氮硫氧化合物含量为38%，环烷烃含量为25%，该石油属于哪类石油？（）

A.石蜡型；

B.环烷型；

C.芳香—中间型；

D.石蜡—环烷型。
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