国家开放大学 / 综合英语（1）
正确率：100%
According to the passage, coins once had real value as currency because they
a.represented a great improvement over barter
b.could become collector's items
c.permitted easy transportation of wealth
d.were made of precious metals
a.represented a great improvement over barter
b.could become collector's items
c.permitted easy transportation of wealth
d.were made of precious metals
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