Suppose "If Zhang Nan and Lin Feng are not volunteers, then Yangmei is a volunteer" is the premise, and "Lin Feng is a volunteer" is the conclusion. For the above conclusions to be true, the prerequisites to be supplemented are:. ['Zhang Nan is a volunteer.', 'Bayberry is not a volunteer.', 'Yangmei and Zhang Nan are both volunteers.', 'Yangmei and Zhang Nan are not volunteers.']