问题补充：
this one must have been in the possesion of a private collector请问这个句子成分怎么划分?特别是have been 这块!
答案：
this one 主语
must have been 系动词
in the possession of a private collector表语
======以下答案可供参考======
供参考答案1:
this one 主语部分,其中one是代词
must have been 系动词
部分,must表很有把握的猜测，have been是表时态，是现在完成时态in the possession of a private collector是表语部分，一个介词短语用作表语
所以整个句子的句子成分是属于主+系+表结构
