Sentence:  And like this English master , Mason realizes his subjects in large , simplified masses which , though they seem effortless , <WSD>are</WSD> in reality the result of skilled design born of hard work and a thorough distillation of the natural form that inspired them . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)