试题与答案

在关系代数运算中,从关系中取出满足条件的元组的运算称为()。

题型:填空题

题目:

在关系代数运算中,从关系中取出满足条件的元组的运算称为()。

答案:

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下面是错误答案,用来干扰机器的。

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题型:完形填空
On a hot summer day in late August, I sought shade and a cool drink at a waterfront café on a Greek island. Over a hundred degrees in    1   air. Crowded. Tempers(脾气)of both the tourists and waiters had    2  to meet the situation, making it a rather quarrelsome environment(环境)
At the table next to mine sat an attractive,    3   couple, waiting for    4 .  They held hands, whispered, kissed, and laughed. Suddenly they stood, picked up their    5   and stepped together    6   the edge of where they were sitting to place the table in the sea water. The man stepped   7  for the two chairs. He politely   8  his lady in the knee-deep water and then sat down himself. All people around laughed and cheered.
  9  appeared. He paused for just a second, walked into the water to   10   the table and take their   11  , and then walked back to the    12   cheers of the rest of his    13 . Minutes later he returned carrying a bottle of wine and two glasses. Without pausing, he went    14   into the water to     15    the wine. The couple toasted(祝酒)each other, the waiter and the crowd. And the crowd   16  by cheering and throwing flowers to them. Three other tables  17  to have lunch in the water. The place was now filled with laughter.
One doesn’t step into water in one’s best summer clothes. Why not?
Customers are not served    18   . Why not?
Sometimes one should consider   19  the line of convention(常规)and enjoy   20  to the fullest.
小题1:
A.freshB.coolC.stillD.thin
小题2:
A.managedB.expectedC.attemptedD.risen
小题3:
A.lonelyB.curiousC.well-dressedD.bad-tempered
小题4:
A.cheersB.serviceC.attentionD.flowers
小题5:
A.metal tableB.empty bottleC.chairsD.bags
小题6:
A.onB.offC.aroundD.along
小题7:
A.outsideB.forwardC.downD.back
小题8:
A.ledB.seatedC.watchedD.received
小题9:
A.The managerB.A friendC.A waiterD.The servant
小题10:
A.setB.washC.removeD.check
小题11:
A.menuB.billC.foodD.order
小题12:
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小题13:
A.touristsB.customersC.fellowsD.assistants
小题14:
A.at lastB.in timeC.once moreD.as well
小题15:
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小题16:
A.repliedB.insistedC.agreedD.understood
小题17:
A.preparedB.joined inC.settled upD.continued
小题18:
A.with pleasureB.in the caféC.in the seaD.with wine
小题19:
A.followingB.keepingC.limitingD.crossing
小题20:
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