回答如下：

where是个副词，在句中作地点状语，它可以作疑问副词、连接副词和关系副词。例如：

疑问副词：Where do you live? 

连接副词： That is where he works. 

                   I know where he lives. 

关系副词：This is the house where Lu Xun once lived.

                   This is our school， where there are about two thousand students.