通信管道、通道与铁路钢轨（或坡脚）的最小平行净距为（）m。

A、2

B、1.5

C、1

D、0.5

Which two statements about sequences are true? （）

You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value.

You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence.

You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence.

You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column.

If a sequence starting from a value 100 and incremented by 1 is used by more then one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence.

You use REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.

Identify three situations in which you would NOT be able to drop a tablespace. （）

when the tablespace is online

when the tablespace has segments with data in it

when the tablespace is a default permanent tablespace for the database

when the tablespace contains a table that is currently being used by transactions

when the tablespace contains undo data that is needed to rollback an uncommitted transaction

安装WINDOWS2000前，要检查下列哪些项目（）

A、与UPS之间的连接

B、第三方软件

C、防病毒软件

D、主板BIOS

用于配置匿名用户的是（）。

A、FTP站点选项

B、主目录选项

C、安全帐户选项

D、目录安全性选项

直放站提取信号源的主要方式有哪几种：（）

A、通过直放站的施主天线直接从附近基站提取信号。

B、用耦合器从附近基站耦合部分信号通过光纤传送到盲区内的直放站。

C、通过直放站的施主天线直接从附近直放站提取信号。

D、用耦合器从附近基站耦合部分信号通过电缆传送到盲区内的直放站。