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问题 选择题

既可防治夜盲症，又可防治佝偻病的食物是                            ( )

A．胡萝卜

B．含钙食物

C．动物肝脏

D．新鲜蔬菜

答案

答案：C

分析：维生素既不参与构成人体细胞，也不为人体提供能量，而且人体对它的需要量很小，但它对人体的各项生命活动有重要的作用；人体一旦缺乏维生素，就会影响正常的生长和发育，还会引起疾病．

解答：解：人体一旦缺乏维生素，就会影响正常的生长和发育，还会引起疾病，如图：

可知缺乏维生素A易患夜盲症、皮肤粗糙等．缺乏维生素D易患佝偻病，即骨软化病．动物的肝脏中含丰富的维生素A和维生素D，既可防治夜盲症，又可防治佝偻病．

故选：C

点评：此题考查了维生素的缺乏症及食物来源．可结合表格中的内容来比较记忆．

填空题


The central problem of economics is to satisfy the people’s and nation’s wants. The problem we are faced with is that our (1) , here identified as money, are (2) . The only way we can resolve our (3) is to make choices. After looking at our resources, we must examine our list of (4) and identify the things we need (5) , those we can postpone, and (6) we cannot afford. As individuals, we face the central problem involved in economics — deciding just how to allocate our limited resources to provide ourselves with the greatest (7) of our wants.
Nations face the same problem. As a country’s population (8) , the need for more goods and services grows (9) . Resources necessary to production may increase, but there are (10) enough resources to satisfy the total desires of a (11) . Whether the budget meeting is taking place in the family living-room, in the conference room of the corporation (12) of directors, or in the chamber of the House of Representatives in Washington, the basic problem still exists. We need to find (13) of allocating limited resources in order to satisfy unlimited wants.
A short time ago, economists divided goods into two categories, free and economic. The former, like air and water, were in (14) abundance that economists had no concern about (15) of scarcity and what to do about it. Today many of these "free goods" are in (16) very expensive to use. Pollution has made clean air and water expensive for producers who have to filter their waste products, for consumers who ultimately pay for the producers’ extra costs, and (17) tax-payers who pay for the government’s involvement in cleaning the environment.
In the 1990s, almost all goods are (18) . Only by effort and money can they be (19) in the form people wish.
Meeting the needs of people and the demands from resources available leads to the basic activity of production. In trying to (20) unlimited wants from limited economic goods, production leads to new problems in economics.
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单项选择题

MS发送给SGSN的Activate PDP Context Request中不包含以下的那种数据？（）

A.PCO

B.APN

C.QOS Request

D.WAP Gateway address
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