<p> 在使用mongodb模块的文件顶部应添加以下哪段代码？( )</p>
<p> <br/> var Db = require('Db').<br/> Connection = require('Connection'),<br/> Server = require('Server); </p>
<p> <br/> var Db = require('mongodb'),<br/> Connection = require('mongodb'),<br/> Server = require('mongodb').listen(3000); </p>
<p> <br/> var Db = require('Db').mongodb,<br/> Connection = require('Connection').mongodb.<br/> Server = require('Server').mongodb;</p>
<p> <br/> var Db = require('mongodb').Db,<br/> Connection = require('mongodb').Connection.<br/> Server = require('mongodb').Server;</p>
