若D是由y=x，x=1，y=0所围成的三角形区域，则二重积分在极坐标系下的二次积分是

短文改错 （满分 5 分）

The Mid-autumn Festival, that is one important traditional festival in China, falls in August 15^th of the lunar calendar every year. It was celebrated both in China and many Asian country. People believe that a full of moon is the symbol of reunion and good luck. This is also a custom to express best wishes to their beloved ones at this particularly time. On that day they usually go back home to have a family get-together, so they appreciate the beautiful moon, enjoyed the typical food---the moon cake. All Chinese have wonderful time at the festival.

氯碱厂电解饱和食盐水制取NaOH溶液的工艺流程示意图如下所示，完成下列填空：

（1）在电解过程中，与电源正极相连的电极上电极反应为______，与电源负极相连的电极附近，溶液pH______（选填“不变”、“升高”或“下降”）．

（2）工业食盐含Ca²⁺、Mg²⁺等杂质，精制过程发生反应的离子方程式为______．

（3）如果粗盐中SO₄^2-含量较高，必须添加钡试剂除去SO₄^2-，该钡试剂可以是______．

a．Ba（OH）₂                b．Ba（NO₃）₂              c．BaCl₂

（4）为了有效除去Ca²⁺、Mg²⁺、SO₄^2-，加入试剂的合理顺序为______（选填a、b、c）

a．先加NaOH，后加Na₂CO₃，再加钡试剂

b．先加NaOH，后加钡试剂，再加Na₂CO₃

c．先加Na₂CO₃，后加NaOH，再加钡试剂．

某站开放出站信号，向施工封锁区间发出路用列车，属于铁路交通一般（）事故。

A、A类

B、B类

C、C类

D、D类

小鹅瘟的典型病变为( )。

A．肠黏膜充血，出血

B．空肠和回肠的急性卡他性一纤维素性坏死性肠炎

C．肝脏肿大，有出血点

D．肝脏、心脏上有纤维素渗出覆盖

E．以上都不是

完整家居的工艺解剖室可以让客户清楚了解到“（）”的全过程。