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问题 选择题

下列物质中既不含有氧元素也不含有氢元素的是（　　）

A．水（H2O）

B．二氧化碳（CO2）

C．金刚石（C）

D．碳铵（NH4HCO3）

答案

A、水是由氢氧两种元素组成的，不符合题意；

B、二氧化碳是由碳氧两种元素组成的，不符合题意；

C、金刚石是由碳元素组成的，符合题意；

D、碳铵是由氮、氢、碳、氧四种元素组成的，不符合题意．

故选C．

填空题

对干熄炉的斜道砖的要求是（）。
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单项选择题

The history of African—Americans during the past 400 years is traditionally narrated (1) an ongoing struggle against (2) and indifference on the part of the American mainstream, and a struggle (3) as an upward movement is (4) toward ever more justice and opportunity.

Technology in and of (5) is not at fault; it’s much too simple to say that gunpowder or agricultural machinery or fiber optics (6) been the enemy of an (7) group of people. A certain machine is put (8) work in a certain way—the purpose (9) which it was designed. The people who design the machines are not intent on unleashing chaos; they are usually trying to (10) a task more quickly, cleanly, or cheaply, (11) the imperative of innovation and efficiency that has ruled Western civilization (12) the Renaissance.

Mastery of technology is second only (13) money as the true measure of accomplishment in this country, and it is very likely that by (14) this under-representation in the technological realm, and by not questioning and examining the folkways that have (15) it, blacks are allowing. (16) to be kept out of the mainstream once again. This time, however, they will be (17) from the greatest cash engine of the twenty-first century. Inner-city blacks in particular are in danger, and the beautiful suburbs (18) ring the decay of Hartford, shed the past and learn to exist without contemplating or encountering the tragedy of the inner city.

And blacks must change as well. The ways that (19) their ancestors through captivity and coming to freedom have begun to loose their utility. If blacks (20) to survive as full participants in this society, they have to understand what works now.

3（）

A.charting

B.charts

C.charted

D.tochart
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