Sentence:  Albert ( 1949 ) has concluded that the most active preparations of TSH made during this period , from 1931 to 1945 , <WSD>were</WSD> probably about 100 to 300 times as potent as the starting material . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)