TOEFL Listening: TPO-TOEFL阅读TPO - ISB4U5VYKFS2FUO9N$

According to paragraph 2, why were tokens eliminated? A. They were not numerous or varied enough to represent all of the trade commodities. B. They were easily broken and then hard to count. C. They were difficult to keep together in batches. D. They were unnecessary when symbols were used on the surface of envelopes.