Trust, which cannot be sustained in the absence of mutual respect, is essential to any long-lasting relationship, personal or professional. However, personal relationships, such as marriage or friendship, additionally require natural affinity. If a personal relationship is to endure, it must be supported by the twin pillars of mutual respect and affinity. If the statements above are true, then which one of the following must also be true? ['In the context of any professional relationship, mutual respect presupposes trust.', 'Basing a marriage on a natural affinity will ensure that it will endure.', 'Personal relationships, such as marriage or friendship, are longer-lasting than professional relationships.', 'A friendship supported solely by trust and mutual respect will not be long-lasting.']