Sentence:  Now when , so to speak , the cream has been skimmed off , and the items in the successful categories separated out , the sitter can be asked to consider and rate only this concentrated `` cream '' , where the sensitive <WSD>is</WSD> at her best . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)