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在关系代数的专门关系运算中，假定有关系R和S，运算结果为W.如果W中的元组属于R，或者属于S，则W为（）运算的结果；如果W中的元组属于R而不属于S，则为（）运算的结果；如果W中的元组既属于R又属于S，则W为（）运算的结果.
A . 笛卡尔积
B . 并
C . 差
D . 交
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气密性检测时压力稳定作用时间为（）s，泄压时间不少于（）s.
A . A、3，3
B . B、3，1
C . C、5，3
D . D、5，1
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水密性检测时压力稳定作用时间为（）s，泄压时间不少于（）s.
A . A、3，3
B . B、3，1
C . C、5，3
D . D、5，1
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( ) is admittedly an autobiographical novel which draws much on Maugham’s own experience.
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When the author asked Spender what he thought was the most beautiful line in the English language, Spender wrote the line of T. S. Eliot.
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Sun Yang’s son wrote a book entitled On the Physiognomy of Horses
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Of Human Bondage is an autobiographical novel of W. S. Maugham.
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( ) is admittedly an autobiographical novel which draws much on Maugham ’ s own experience .
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W. H. Auden’s poetry is always hard to understand and difficult to imitate.
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Of Human Bondage is a n autobiographical novel of W. S. Maugham .
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W. Shakespeare’s first historical tetralogy include_____.
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听力原文：Technicians are making the last-minute preparations for the launch of the U. S. s
听力原文： Technicians are making the last-minute preparations for the launch of the U. S. space shuttle Discovery on a flight to the International Space Station. Flight officials with the space agency NASA are aware of storm clouds near the Atlantic coast launch site in Florida, which could postpone the launch. This is the second shuttle flight since Columbia disintegrated on reentry three years ago, killing all seven astronauts on board. Since then NASA has spent hundreds of millions of dollars to correct design flaw that caused a piece of foam insulation to break off from the fuel tank and puncture Columbia's wing. NASA is launching Discovery despite objections by the space agency's chief safety officer and chief engineer. They say the problems with the foam insulation have still not been resolved. Shuttle astronaut Steve Robinson says he is not worried. "The thing like this happened to every single flight and what's really great -- you remember how much we talked about culture change after Columbia. This is culture change. You are seeing it."
The space agency's chief safety officer ______ NASA's plan to launch Discovery.
A．vetoed
B．sanctioned
C．supported
D．disapproved
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对于旋分器的入口线速中规定，一级入口大于（)m／s，不得低于15m／s.
A、10
B、15
C、20
D、25
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设S为集合且A=P（S)-（S.ɸ)≠ɸ,求的极小元，极大元，最小元及最大元。
设S为集合且A=P(S)-(S.ɸ)≠ɸ,求<img src='https://img2.soutiyun.com/ask/2020-07-29/96488034135717.png' />的极小元，极大元，最小元及最大元。
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如图 6－19（a)所示，一空气平行板电容器,两极板的面积为S,相距为d。将一厚度为d／2.面积为S.相对
如图 6-19(a)所示，一空气平行板电容器,两极板的面积为S,相距为d。将一厚度为d/2.面积为S.相对介电常数为<img src='https://img2.soutiyun.com/ask/2020-05-09/957865321390217.png' />的电介质板平行地插入电容器,忽略边缘效应，试问:
(1)插入电介质板后的电容变为原来电容Co的多少倍？
(2)如果平行插人的是与介质板厚度、面积均相同的金属板则又如何？
(3)如果平行插人的是厚度为t.面积为S/2的介质板,位置如图6-19(b)所示,电容变为多少？
<img src='https://img2.soutiyun.com/ask/2020-05-09/957865330805342.png' />
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What did Dr. Jason s students do when he wrote a second edition？
A．They kept parts of the old edition.
B．They switched entirely to a new book.
C．They kept away from any new book.
D．They bought the new book at a discount.
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Emily Dickinson wrote 1775 poems, but only ____ of which had appeared during her life time. （）
A．7
B．9
C．1
D．12
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After George W. Bush, Sr. 's success in 1988 Presidential campaign, the junior gathered the group of partners______.
A．to start the preparations for his own campaign for US presidency
B．to buy the Texas Rangers baseball franchise
C．to begin a career in the energy business
D．to study for a Master of Business Administration
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The man was their mother' s friend, not their father' s.
<img src='https://img2.soutiyun.com/ask/uploadfile/4215001-4218000/a0f41db48645ff73fd6a04c0be089133.gif' />
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In the 1920s and the 1930s,the short story, as a form, was difficult to sell. Readers found it an awkward compromise between a poem and a longer novel. The long-short story or novella was scarcely known. Certain comic geniuses like P. G. Wodehouse found it easy to reach and keep a vast public with short stories, either alone or in series. And of course there was W. Somerset Maugham. But the less accomplished writers found the market dwindling even further.
Since 1945, the entire literary picture has changed. Fiction of ail kinds, but above all the short story, has become more and more uneconomic to publish. Many magazines have gone out of business. As a type, the "man of letters", puffing a pipe, has almost vanished, to be replaced by the university lecturer or the television scriptwriter. The public is not attracted by imaginary plots in books but prefers the actual, the real story of real people. For those who do not read at all, television provides an enticing alternative.
Such a decline is in many ways a sad one because the old-time short story had a human quality about it which is now eroded. Yet, in an odd way, in our chaotic electronic age, the short story still has a prospect of living. It has been discovered by film scriptwriters that the form. of the short story provides a useful structure for television; it readily provides the basis for a one-hour programme.
The best title for this passage is ______.
A．The Short Story and Television
B．The Short Story and the Public
C．The Short Story: Past and Present
D．The Short Story: Form. and Content
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证明药粉s在两种不互溶的液体a和β中的分布:（1)当σs.β＞σs.a+σa.β，s分布在体a中。（2)当σa.β＞σs.β+σs.β，S分布在液体a、β之间的界面上.
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仔细阅读下列算法,则最后输出的 n , S 的值分别为（） 第一步 n= 1 , S =0; 第二步 n=n+ 1 , S = S + n ; 第三步 n=n+ 1 , S = S × n ; 第四步 输出 n , S.
A．3 ，5
B．3 ，3
C．3，6
D．3,2
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Excuse me, where’s the bank？ It’s next to the newsagent’s.（)
是
否
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We found Marry’s brother to have _____ more story books than Ann’s.
A．much
B．too much
C．by far
D．far
