肺栓塞在肺显像中典型表现是（）。 A.灌注显像有缺损，通气显像正常 B.灌注显像通气

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.

实验中学某化学兴趣小组，用氢氧化钠（NaOH）吸收二氧化硫的方法，通过计算测定县城空气中二氧化硫的含量，反应的化学方程式为2NaOH+SO₂═NaSO₃+H₂O．现用足量的氢氧化钠溶液充分吸收1000L空气中的二氧化硫（假设该空气中的其它成分与氢氧化钠溶液不反应，也不会引起溶液增重），发现氢氧化钠溶液增重0.64g．若该空气的平均密度为1.28g/L，试计算：

（1）参加反应的氢氧化钠的质量．

（2）该空气中二氧化硫的质量分数．

胃肠解痉药服用

A．1：(2000～5000)高锰酸钾溶液
B．药用炭二份，鞣酸、氧化镁各一份的混合物5g加温水500ml
C．3%过氧化氢溶液10ml加入100ml水中
D．1%～2%氯化钠溶液或生理盐水
E．3%～5%鞣酸溶液上述洗胃液中：

减慢舒张期时心血管生理上有什么变化（）

A.左心室血液缓慢充盈到主动脉

B.心房缓慢被充盈

C.心房血液缓慢而最后全部充盈到左心室

D.心房血液快速充盈到左心室

E.左心房血液在舒张时相的中期缓慢充盈到左心室

在燃烧室内工作需加强照明时，可由电工安设110、220V临时性的固定电灯，电灯及电线须绝缘良好，并安装牢固，放在人碰不着的高处，安装后必须由检修工作负责人检查。（）带电移动110、220V的临时电灯。

A.禁止

B.可以

C.不宜