什么XPath查询将选择< media：thumbnail />节点在以下XML？
<item> <title>Sublime Federer crushes Wawrinka</title> <description>Defending champion Roger Federer cruises past Stanislas Wawrinka 6-1 6-3 6-3 to take his place in the Australian Open semi-finals.</description> <link>http://news.bbc.co.uk/go/RSS/-/sport2/hi/tennis/9372592.stm</link> <guid isPermaLink="false">http://news.bbc.co.uk/sport1/hi/tennis/9372592.stm</guid> <pubDate>Tue,25 Jan 2011 04:21:23 GMT</pubDate> <category>Tennis</category> <media:thumbnail width="66" height="49" url="http://news.bbcimg.co.uk/media/images/50933000/jpg/_50933894_011104979-1.jpg"/> </item>
XML来自这个RSS feed.
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