Sentence:  `` We could put up cribs on the second floor sleeping porch and turn the front bedroom into a playroom where it 's nice and sunny , but of course it would entail quite a bit of running up and down stairs and Chris said you were to <WSD>be</WSD> careful about that '' . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)