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问题 选择题

如图所示，物体沿两个半径为R的半圆弧由A运动到C，则它的位移和路程分别是（　　）

A．0，0

B．4R向东，2πR向东

C．4πR向东，4R

D．4R向东，2πR

答案

物体运动的起点是A，终点是C，则位移大小等于AC，大小x=4R，方向向东．路程S=2πR．

故选D

选择题

真分数□1，□里应填[ ]

假分数□1，□里应填[ ]

A．大于

B．小于

C．等于

D．大于或等于
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单项选择题

The relational database model requires the data be (110) through programs that don’t rely on the position of the data in the database. This is in direct (111) to the other database mode, where the program has to follow a series of pointers to the data it seeks. A program (112) a relational database simply asks for the data it seeks; the DBMS performs the necessary searches and (113) the information. The (114) on how the search is done are specific to the DBMS and vary from product to product.

（112）是（）

A.consulting

B.containing

C.querying

D.queuing
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