Zachary has been trying to work on an essay for almost three hours, but he can't seem to focus for more than 15 or 20 minutes at a time. what should he do so that the quality of his work doesn't suffer because of poor concentration and lack of energy?

a-push through his mental block and keep going until he finishes his essay
b-put the essay away and don't work on it for a few days
c-turn on the tv so that it'll wake him up enough to finish his essay
d-finish what he's working on and then stop so he can start fresh tomorrow