Sentence:  While some suppression and some denial <WSD>are</WSD> not only necessary but healthy , the worker 's clinical knowledge must determine how these defenses are being used , what healthy shifts in defensive adaptation are indicated , and when efforts at bringing about change can be most effectively timed . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)