题目内容
某项目现有甲、乙两个方案，各方案的费用分别为450万元、550万元，各方案的功能得分及重要度权数见下表，优选方案为()。
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若A、B、C、D、E五名运动员进行乒乓球循环赛(即每两人赛一场)，比赛进行一段时间后，进行过的场次数与队员的对照统计表如下：
那么与E进行过比赛的运动员是()。
The author's main purpose in writing this passage is most probably to______.
In the third paragraph the author explains______.
It would be difficult to have a society like ours without public goods such as defense, transportation, and other services.
A public good is one that a person can use without reducing the use of it for another person. One of the best example of a public good is national defense. One person can benefit form. our national defense without reducing another person's benefits. In fact, it is difficult to keep any person in our society from enjoying the benefits of national defense.
The market system does not work well in producing public goods. This is because a person who refuses to pay for a public good cannot be kept from using it. Suppose that the neighbors in a high crime area decide to hire a police force. Each neighbor, except Mrs. Smith, agrees to pay $100 a year for it. Mrs. Smith refuses to pay because she knows that if all the others pay the $100, the police will guard the area anyway. So Mrs. Smith can enjoy the services of the police force without paying $100.
The market system has no way to deal with this type of problem. For this reason, we cannot ask each person to make a direct payment in the form. of product price. Therefore, we collect money for public goods by using taxes.
According to the passage, public goods are______.
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