试说明推动分时系统形成和发展的主要动力是什么？

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• A user is currently running Windows XP Media Center 32-bit and wants to upgrade to WindowsVista. An in-place upgrade is required. Which of the following versions can be used to accomplish this?（）

  A、Windows Vista Home Premium

  B、Windows Vista Home Basic

  C、Windows Vista Ultimate 64-bit

  D、Windows Vista Business 64-bit

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• 在PowerPoint中，幻灯片放映时要有对象进入放映界面的动画效果，应选择（）动画效果设置。

  A、 进入

  B、 强调

  C、 退出

  D、 动作路径

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• What does the TRUNCATE statement do?（）

  A、Removes the table

  B、Removes all rows from a table

  C、Shortens the table to 10 rows

  D、Removes all columns from a table

  E、Removes foreign keys from a table

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• The EMP table contains these columns: LAST NAME VARCHAR2(25) SALARY NUMBER(6,2) DEPARTMENT_ID NUMBER(6) You need to display the employees who have not been assigned to any department. You write the SELECT statement: SELECT LAST_NAME, SALARY, DEPARTMENT_ID FROM EMP WHERE DEPARMENT_ID = NULL; What is true about this SQL statement? （）

  A、The SQL statement displays the desired results.

  B、The column in the WHERE clause should be changed to display the desired results.

  C、The operator in the WHERE clause should be changed to display the desired results.

  D、The WHERE clause should be changed to use an outer join to display the desired results.

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• 制图国家标准规定，图纸幅面尺寸应优先选用（）几种基本幅面尺寸。

  A、3

  B、4

  C、5

  D、6

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