国家 * * 习 * * 在博鳌亚洲论坛2015年年会开幕式上发表了题为《迈向命运共同体开创亚洲

一个圆弧形拱桥的跨度为6m，桥的拱高为1m，则此拱桥的半径是（    ）m。

绿肥的施用应注意哪些问题

哪项不是职业病特点( )

A．病因明确
B．存在剂量-反应关系
C．多为群发性
D．需用特殊治疗方法
E．可以预防

Today I’d like to talk about how to become a (1) . Usually you have to start at the beginning. That is, you have to begin (2) of some sort on a local newspaper, a (3) , maybe on a small magazine -- work (4) . Now there aren’t that many organizations which have large numbers of foreign correspondents so you also have to (5) with that aim (6) . Another way of doing it is to work abroad, and work as (7) . That’s somebody who sells stories, and gets paid (8) , to newspapers and magazines and so on. And hoping to (9) that way, and eventually to be offered a (10) .
I don’t really know (11) are needed, but obviously a degree in modern languages or (12) would be very useful. But, a degree in itself probably wouldn’t (13) . It wouldn’t be enough to get you job. It wouldn’t (14) to make an editor decide to (15) . So it’s difficult to define the (16) . You’re going to need (17) and the ability to assimilate information (18) and then produce stories which (19) of the newspaper or radio or television station you (20) .

由熔盐电解法获得的粗铝含有一定量的金属钠和氢气，这些杂质可采用吹气精炼法除去，产生的尾气经处理后可用钢材镀铝。工艺流程如下

（注：NaCl熔点为801℃；AlCl₃在181℃升华）

（1）精炼前，需清除坩埚表面的氧化铁和石英砂，防止精炼时它们分别与铝发生置换反应产生新的杂质，相关的化学方程式为①_________________和②___________________。

（2）将Cl₂连续通入坩埚中的粗铝熔体，杂质随气泡上浮除去。气泡的主要成分除Cl₂外还含有_______；固态杂质粘附于气泡上，在熔体表面形成浮渣，浮渣中肯定存在___________。

（3）在用废碱液处理A的过程中，所发生反应的离子方程式为______________________。

（4）镀铝电解池中，金属铝为______极，熔融盐电镀中铝元素和氯元素主要以AlCl₄^-和Al₂Cl₇^-形式存在，铝电镀的主要电极反应式为___________。

（5）钢材镀铝后，表面形成的致密氧化铝膜能防止钢材腐蚀，其原因是___________________。