How the pigment known as Han purple was synthesized by the ancient Chinese of the Qin and Han dynasties has puzzled scientists. The Chinese chemists employed the same chemical ingredients used for Han purple in the production of a common type of white glass during that period. Both were produced in processes that involved subjecting the mixtures to high heat and mixing in lead to decrease the melting temperature. Thus, Han purple was probably discovered by fortuitous accident during glass production. Which one of the following, if true, would most strengthen the argument? ['Chemical analysis shows that most of the known fragments of both Han purple and the white glass were produced within a small geographical radius.', 'The technique used for producing Han purple was known to very few people during the Qin and Han dynasties.', 'The ingredients used in producing both Han purple and the white glass were easily obtainable during the Qin and Han dynasties.', 'The white glass is found in more surviving artifacts from the Qin and Han dynasties than Han purple is.']