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问题 选择题
若平面上点（x，y）在直线x+2y=3上移动，则2x+4y的最小值是（　　）
A．
2
B．
22
C．
23
D．
42
答案

∵2x+4y≥2

2x•4y
=2
2x+2y

又∵x+2y=3

∴2x+4y≥2

2x•4y
=2
2x+2y
=2
23
=4
2

当且仅当2x=4y即x=2y=

3
2
时取等号

故选项为D

选择题

现有下列物质 ①2.3g Na ② 6.2g Na2O ③7. 8g Na2O2 ④ 4.0g NaOH，把它们分别放入100g水中，对所得的溶液的质量分数中正确的是

A．③＞②＞①＞④

B．③＝②＞①＞④

C．④＞③＞②＞①

D．③＝②＞④＝①
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阅读理解
For many in the United States,Arab-Americans are an invisible part of the population．Though Arab-Americans as a community have made great contributions to American society in fields from literature to politics to medicine,many Americans know very little about Americans of Arab backgrounds．
Arab history in the United States goes back to the late 1800’s when large numbers of Arab immigrants first began making their journey to a land known simply as“Amreeka”．
Historians generally describe Arab immigration to America in two waves．The first wave took place between 1860 and 1924．The first wave consisted of Lebanese and Syrian,and some Egyptian immigrants．These new immigrants,who were mostly Christian,came to America in search of better opportunities．Even the doomed Titanic,which set sail for America in 1912,had close to a hundred Arab passengers aboard．The majority of Arab-Americans today are descendents of the first wave of immigrants;they are the third or more generation Americans．
The second wave of immigrants followed after World War Ⅱ,caused by political unrest in the Middle East．This second wave of immigrants consists of mainly Arab Muslims（穆斯林）and continues to this day．
Arab-Americans make up 3 million of the population in the United States,according to demographers．And quite different from popular belief,64 percent of them are American-born．Eighty-two percent of Arab-Americans are US citizens．
Arab-Americans are beyond the national average in both education and income．Education is important among Arab-Americans;82 percent have high school diplomas,36 percent have bachelor’s degrees or higher,and 15 percent have graduate degrees．The-median（中位数的） average income among Arab-Americans is $39 580,which is higher than the US average．
小题1: What would be the best title for the text?
A．Arabs in America．B．The Two Arab Immigration Waves to America．
C．Arab-Americans,Contributions to America．
D．Arab-Americans,Education and Income．
小题2:The first wave of immigrants took place because______．
A．all Arabs were Christian at that time
B．Arabs wanted to hunt for a better development
C．the Second World War broke out
D．Arabs wanted to gain higher income
小题3:The writer of this passage mentioned Titanic______．
A．to tell us that taking ship at that time was dangerous
B．because Titanic became a well-known disaster
C．to show us there were many Arabs flocking into America at that time
D．to inform us that Arabs are brave enough
小题4:From the last paragraph we can infer that______．
A．Arab-Americans are much more clever than native Americans
B．Arab-Americans are hard-working people
C．the higher education you receive,the higher income you will get in America
D．Arab-Americans play the most important role in the American average in both education and income
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