Sentence:  Then , too , the utmost clinical flexibility <WSD>is</WSD> necessary in judiciously combining carefully timed family-oriented home visits , single and group office interviews , and appropriate telephone follow-up calls , if the worker is to be genuinely accessible and if the predicted unhealthy outcome is to be actually averted in accordance with the principles of preventive intervention . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)