Sentence:  Mrs. Reavey 's work is written for the stage - it is mentioned for an off-Broadway production in the fall - and , in addition , employs an avant-garde structure that particularly needs to be seen if comprehension <WSD>is</WSD> to be encouraged . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)