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问题 单项选择题

与域演算表达式{ab|R（ab）∧R（ba）}不等价的关系代数表达式是（）。

A．π1,2 (σ1=4∧2-3 (R×R)

B．π1,2

C．R∩π2,1 (R)

D．σ1=2 (R)

答案

参考答案：D

选择题

下列各句中画线的词语，使用不恰当的一句是[ ]

A．影视明星代言虚假广告虽为舆论所不耻，但身为公众人物的他们依然乐此不疲，其中很重要的原因是他们可以轻易找到借口，开脱责任。

B．迪拜世界债务危机的爆发在短期内引发了连锁反应。但是当市场意识到迪拜世界不过是旧危机的涟漪，而非新危机的滥觞之时，市场也就会回归理性，一切仍将回到V形反弹的轨道上。

C．美国国务卿希拉里在参观中美合作的背景太阳宫热电厂时说，解决环境污染问题不能临渴掘井，不希望中国重复美国在工业化进程中犯过的错误。

D．2010年3月7日晚，第82届奥斯卡金像奖尘埃落定，由美国电影导演凯瑟琳·毕格罗执导的《拆弹部队》夺得包括最佳影片、最佳导演奖在内的五项大奖，她也成为了首位奥斯卡最佳女导演。
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单项选择题

第1篇 Food for Learning


In Eritrea, a small country in northeast Africa, approximately 80 percent of the population is illiterate. That percentage is even higher in woman. As in many developing countries, many Eritreans have traditional ideas about the role of women. They believe that women should stay home and take care of the family and should not get an education or look for a job.
These beliefs are one of the factors that prevent Eritriea and other developing countries from improving their economic situation. Experience in many developing countries has shown that educated women have fewer children and have more opportunities for improving their lives and the lives of their families. In Eritrea, in fact, there is great need for improvement. It is one of the poorest countries in the world. For many Eritrean families, getting enough food is a daily problem.
To deal with these problems, the Eritrean government together with the World Food Program, has a new program that offers food as a reward for learning. In primary schools, all the children receive food packages to take home to their families. However, with the new program, the girls receive more food than the boys. This way, parents are encouraged to send their daughter to school rather than keeping them at home.
Another government program that aims to educate women is Food for Training. Managed by the National Union of Eritrean Women, this program offer food rewards (also from World Food Organization) to women and elder girls who are willing to join the program. Because of the war with Ethiopia, many women are bringing up their families on their own. They often live in refugee camps, with no land of their own and no way to earn money. Most of these women are illiterate and have no skills to find a job. They spend most of their day looking for food and preparing it for their families.
The Food for Training program helps the teenagers and women change their lives. If they agree to join the program, they receive a large package of food each month. In return, the women are required to attend free literate classes for two hours every day. When Food for Training classes in two regions of Eritrea, 5000 girls and women joined in the first two months. It is especially popular with teenage girls, aged fourteen to sixteen, who have never had a chance to go to school before.
The organizers of Food for Traing also plans to offer other kinds of courses for women, using the same system of food rewards. In these courses, they will teach women job skills and crafts such as basket weaving. These women will not only learn to read and write. They will become aware of what is going on in their country.

The Eritrean government is offering extra food to girls in school in order to ______.

A．encourage to keep girls at home

B．change traditional attitudes towards women

C．help girls feed their families

D．creat more jobs for Eritrean teachers
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