对关系数据库来讲，下面( )说法是错误的。A．每一列的分量是同一种类型数据，来自同一

International free trade occurs when there are no barriers to trade. Countries can get a lot of benefits from free trade. (31) , all countries choose to adopt protection policies to some extent In this essay, I will give (32) of the arguments in favour of world free trade, describe the methods for the trade protection policies (33) countries erect to protect domestic industries and give the arguments which can be put (34) to justify protectionist policies.
Tariffs are taxes on (35) products. Sometimes, tariffs are known (36) imports duties and customs duties. They can be used (37) raise revenue. But, they are usually used to (38) imports and also to help domestic producers. The effect of imposing (39) tariff is to raise price for domestic consumers, and some consumers will switch consumption (40) imported goods to domestically produced substitutes. (41) are two types of tariffs. One is percentage taxes, it is based on
percentage of value of goods. (42) one is specific (fixed sum taxes), it is based on a fixed tax (43) unit or weight. Quota is a limit on the supply of goods or services. It can be imposed on exports. The domestic market share will increase because of (44) a limit on the quantity of imported goods. However, the price of protected goods will also rise because a quota is to reduce supply. Voluntary export restraint or restriction (45) similar to a quota, but this time the limit on imports arises from a voluntary agreement (46) the exporting and importing countries. For example, the UK had an agreement with Japanese car (47) that they should not take (48) than 10 percent of the UK car market. Exchange control means that a government control on foreign currency controls importers access to foreign currency. This is a (49) which was used by a number of European countries, (50) the UK, in the 1960s and 1970s and is still found in some developing countries.

豆纹动脉由哪支动脉发出（）

A.颈内动脉

B.大脑前动脉

C.大脑中动脉

D.大脑后动脉

E.基底动脉

系统内资金调拨要按照规定提出（），实行审批制度，严禁逆程序操作。

A.口头申请

B.电话申请

C.邮件形式

D.书面申请

根据《SDH长途光缆传输系统工程验收规范》，安全检查：

1．机房防火应符合设计要求。

2．机房内必须配备有效的灭火消防器材。凡要求设置的火灾自动报警系统和固定式气体灭火系统，必须保持性能良好。

3．楼板顶预留孔洞应配置阻燃材料的安全盖板。

4．机房内严禁存放易燃、易爆等危险物品。