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问题 选择题

Jack didn't do his homework, but he     to the teacher that he had       it at home. [ ]

A. lied; forgotten

B. lay; left

C. lay; forgotten

D. lied; left

答案

答案：D

单项选择题

设两个关系C和SC如下，它们的主键分别为C#和(S#，C#)，在关系SC中除属性 GRADE的数据类型是整型，且允许空值外，其他属性的数据类型都是字符型。若要向关系SC执行插入操作，下面给出的4个元组中哪一个元组可以被插入　　　　　　　　　　　　　　　　　　　　　　　　　C

A．C#

B．CNAME

C．TEACHER

D．C1

E．database

F．zhang

G．C2

H．network

I．ling

J．C3

K．os

L．wu
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单项选择题

It is widely assumed that a museum is helped financially when a generous patron donates a potential exhibit. In truth, however, donated objects require storage space, which is not free, and routine conservation, which is rather expensive. Therefore, such gifts exacerbate rather than lighten the demands made on a museum’s financial resources.
Which of the following, if true, most seriously weakens the argument above

A．To keep patrons well disposed, a museum will find it advisable to put at least some donated objects on exhibit rather than merely in storage.

B．The people who are most likely to donate valuable objects to a museum are also the people who are most likely to make cash gifts to it.

C．A museum cannot save money by resorting to cheap storage under less than adequate conditions, because so doing would drive up the cost of conservation.

D．Patrons expect a museum to keep donated objects in its possession rather than to raise cash by selling them.

E．(E) Objects donated by a patron to a museum are often of such importance that the museum would be obliged to add them to its collection through purchase if necessary.
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