Sentence:  In addition to the basic programs in wavelength standards , spectroscopy , solid state physics , interactions of the free electron and atomic constants which <WSD>are</WSD> necessary to provide the foundation for technological progress , the Bureau has strengthened its activities in laboratory astrophysics . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)