<p>Some people believe that spending solitary, quiet hours reading and thinking in a library [is/are] the best way to prepare for a debate tournament.</p>
<p>Which is correct and why?</p>
<p>The answer is “is” because it modifies “the best way” which is a singular concept.</p>
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<p>Although the answer is “is”, it is not a great idea to look at “the best way” to determine this. In English the verb agrees with the subject, not with the predicate. “Is” agrees with “spending” which is the noun “is” is agreeing with.</p>