三相三线有功电能表能准确测量（）的有功电能。 对称三相三线电路。 三相四线电路。 不完全对称三相电路。 三相电路。
注释是一些说明性的文字，而不是（）语句，不参与程序的编译。
发展中国家跨国直接投资的优势有哪些？
Your company has a main office and one branch office. All servers run Windows Server 2003 Service Pack 2 （SP2）.In the main office， a server named DNS1 hosts the primary DNS zone for contoso.com.You configure a primary zone for west.contoso.com on a DNS server named DNS2 in the branch office. All servers in the branch office are configured to have the west.contoso.com DNS suffix.You need to ensure that users in the main office can resolve server names in the branch office. The solution must meet the following requirements： （1）Minimize the amount of DNS zone transfer traffic between the offices. （2）Maintain the current name resolution process for users in the main office. What should you configure on DNS1？（） a host record for DNS2。 a secondary zone for the west.contoso.com zone。 a stub zone for the west.contoso.com zone。 DNS2 as a forwarder。
SQL Server支持两种形式的变量，即（）和（）。
公司A使用位于SQL1 服务器上的任务关键级数据库DB1。你要将DB1镜像到另外一个服务器SQL2上。在你建立数据库镜像前，需要为DB1和服务器做好镜像前的准备。你需要执行以下哪三项操作？（）
