把下列单词填入每个句子的空白处（注意所填单词的形式变化）： 1 ___________ is a kind of natural phenomenon.
2 Please read the __________ on the bottle before taking the medicine.
3 May and I are classamtes, but we live in different _________.
4 Mao Zedong spoke with a strong Hunan __________.
5 When we met many years later I could hardly __________ Lily at the airport.
6 Gansu is a __________ province of China.
7 If you want to learn Chinese, you may learn from her. She speaks very ________ Chinese.
8 Will you please __________ the story to the whole class?
9 Visitors are ___________ not to touch the exhibits.
10 He lived in America for five years and has a good __________ of English.
11 The population of that country is increasing ___________.
12 Our __________ must do something to stop the rising house prices.
13 The police are trying to discover the __________ of the killer.
14 Usually you will read faster if you have a bigger English _________.
15 All those _________ at the meeting are high officials.
16 _________, English is not so hard to learn if you put your heart into it.
17 _________ speakers of English are in good demand in our school.
18 Only ten boys passed the exam, _________ Peter and you.
19 My father likes me to major in __________ trade when I go to university.
20 , while Americans say ____________.
22 India was once __________by Britain and won its independence in 1947.
（1分） ，其中溴元素的化合价为⑵
（1分） －1 （1分） 。
实验室用乙醇和浓硫酸加热反应制取乙烯，其原理为：