xml中出现“文档中根元素后面的标记必须格式正确。”的错误

出现这个错误的原因是，没有加根节点。请看下面的代码：

<?xml version="1.0" encoding="GB2312" standalone="no"?><time>//如果这里和结尾的</time>不加，就会出现如题的错误<monday><playGameTime>5.0</playGameTime><studyTime>3.0</studyTime><readTechnologyTime>0.0</readTechnologyTime><officialTime>0.0</officialTime><otherTime>0.0</otherTime><efficiency>0.0</efficiency><state>ok</state></monday><tuesday><playGameTime>5.0</playGameTime><studyTime>3.0</studyTime><readTechnologyTime>0.0</readTechnologyTime><officialTime>0.0</officialTime><otherTime>0.0</otherTime><efficiency>0.0</efficiency><state>ok</state></tuesday></time>