Sentence:  But then , after the little operetta had been given its feeble amateur rendering , everyone insisted that it was too good to <WSD>be</WSD> lost forever , and that the Royal Academy of Music must now have the manuscript in order to give it the really first-rate performance it merited . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)