Sentence:  When 1 ml of conjugate was passed through a column ( * * f ) , the first and second milliliter fractions collected <WSD>were</WSD> the most specific and gave no nonspecific staining in some experiments , and very little in others . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)