document.write ("<b>上一篇</b>：<a href='/DocHtml/699/2014/5/4/4745893134662.html'>2.2 我们怎样区分声音</a><br><b>下一篇</b>：<a href='/DocHtml/699/2014/4/7/1409894634658.html'>Unit 2  I can dance</a>")