Sentence:  Incapable of self-delusion , the Founding Fathers found the crisis of their time to <WSD>be</WSD> equally grave , and yet they had confidence that America would surmount it and that a republic of free peoples would prosper and serve as an example to a world aching for liberty . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)