没错,has been是对的.
这题应该是这样:It has been ten years since we last met in Beijing.

英文里有这样一个传统:
通常遇到since+过去式时,将has been改为is.这样比较符合他们口语的规矩.

所以第一个空写is比较地道.
也就是It is ten years since we last met in Beijing.

当然你的has been语法上是对.