Sentence:  His parents talked seriously and lengthily to their own doctor and to a specialist at the University Hospital - Mr. McKinley was entitled to a discount for members of his family - and it was decided it would <WSD>be</WSD> best for him to take the remainder of the term off , spend a lot of time in bed and , for the rest , do pretty much as he chose - provided , of course , he chose to do nothing too exciting or too debilitating . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)