Over 40, 000 lead seals from the early Byzantine Empire remain today. Apart from the rare cases where the seal authenticated a document of special importance, most seals had served their purpose when the document was opened. Lead was not expensive, but it was not free: most lead seals would have been recast once they had served their purpose. Thus the number of early Byzantine documents sealed in such a fashion must have been many times the number of remaining lead seals. Which one of the following statements, if true, most strengthens the argument? ['Most of the lead seals produced during the early Byzantine Empire were affixed to documents that have since been destroyed.', 'During the time of the early Byzantine Empire there were fewer than 40, 000 seals affixed to documents at any given time.', 'Most of the lead seals produced during the early Byzantine Empire were affixed to documents that were then opened during that period.', 'During the time of the early Byzantine Empire there were at most 40, 000 documents of enough importance to prevent the removing and recycling of the seal.']