Sentence:  Recent interferometer measurements ( Radhakrishnan and Roberts , 1960 ) have shown the 960 - Mc emission of Jupiter to <WSD>be</WSD> partially polarized and to originate in a region of larger diameter than the visible disk . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)