定语从句which省略问题?!

问题描述:

定语从句which省略问题?!
Fourth on the list was "stock", (which is)not surprising with Shanghai shares having risen 97 percent last year after doubling the previous year.
其中“not surprising with Shanghai shares having risen 97 percent last year after doubling the previous year. ”应该是一个非限制性定语从句,为何“which is”可省略?不是说“which”在非限制性定语从句中不是宾语就不能省略吗?
那是不是这种情况都可以省略呢?!

需要注意的是,这里省略的是which is,而不是which.这种情况是可以的,例如:The boy,not knowing what to do,turned to his teacher for help.