阅读理解。

    These days most people in Britain and the U. S. A. do not wear very formal clothes. But sometimes it is

important to wear the right clothes.

     Many British people don't think about clothes very much. They just like to be comfortable. When they

want to enjoy themselves, they can wear almost anything. At theaters, cinemas and concerts you can wear

whatever you like. From beautiful suits and dresses to jeans and sweaters. Anything goes as long as (只要)

you look clean and tidy.

     But in Britain and the U. S. A., men in offices usually wear suits and ties, and women wear dresses or

skirts(not trousers). Doctors and business people always wear quite formal clothes. And in some hotels and

restaurants men have to wear ties and women have to wear tidy dresses.

     In many ways, Americans are less formal than British people, but they are more careful with their clothes.

At home or on holidays, most Americans wear uniforms or sports clothes. But when they go out in the

evening, they like to look nice. But in good hotels and restaurants, men have to wear jackets and ties, and

women wear pretty clothes. 

     It's hard to say exactly what people wear in Britain and the U. S. A., because everyone is different. If you

are not sure what to wear, watch first and then do the same. You'll feel more comfortable if you don't look

too different from everyone else.

1. People in Britain and the U. S. A. wear informal clothes when they ____. [ ]

A. go out to enjoy themselves

B. are in offices

C. are in big restaurants

D. go out to work

2. At concerts, doctors wear ____. [ ]

A. sweaters

B. whatever they like

C. what others wear

D. like players

3. Which of the following is not true according to the passage? [ ]

A. Women are usually not allowed to wear trousers in offices.

B. Officers always wear formal clothes even though they are at home.

C. Americans are more relaxed in their clothes than British people.

D. Though everyone is different, they wear the same clothes in offices.

4. "Anything goes" in the second paragraph means "____". [ ]

A. Any clothes are all right

B. Anything wears

C. All the things around are all right

D. Not any clothes are all right

5. Men wear ties when they ____ in the U. S. A. [ ]

A. meet their families

B. meet their close friends

C. eat something delicious

D. have dinner in good restaurants

单晶硅是信息产业中重要的基础材料。通常用炭在高温下还原二氧化硅制得粗硅(含铁、铝、硼、磷等杂质)，粗硅与氯气反应生成四氯化硅（反应温度450~500℃），四氯化硅经提纯后用氢气还原可得高纯硅。以下是实验室制备四氯化硅的装置示意图。

相关信息如下：①四氯化硅遇水极易水解； ②硼、铝、铁、磷在高温下均能与氯气直接反应生成相应的氯化物；③有关物质的物理常数见下表

请回答下列问题：

（1）写出装置A中发生反应的离子方程式____________________。

（2）装置A中g管的作用是____________________；装置C中的试剂是____________________；装置E中的h瓶需要冷却的理由是____________________。

（3）装置E中h瓶收集到的粗产物可通过精馏（类似多次蒸馏）得到高纯度四氯化硅，精馏后的残留物中，除铁元素外可能还含有的杂质元素是__________（填写元素符号）。

（4）为了分析残留物中铁元素的含量，先将残留物预处理，使铁元素还原成Fe²⁺，再用KMnO₄标准溶液在酸性条件下进行氧化还原滴定，反应的离子方程式是：5Fe²⁺＋MnO₄^-＋8H⁺==5Fe³⁺＋Mn²⁺＋4H₂O

①滴定前是否要滴加指示剂？____（填“是”或“否”），请说明理由____________________。

②某同学称取5.000g残留物后，经预处理后在容量瓶中配制成100 mL溶液，移取25.00 mL试样溶液，用1.000×10^-2 mol/L KMnO₄标准溶液滴定。达到滴定终点时，消耗标准溶液20.00 mL，则残留物中铁元素的质量分数是_____________。