Test analysis: a meets the meaning of the question. Gold and silver are products of human labor and can be traded in the New York Mercantile Exchange. B Wrong, different goods have different use values. C skill is correct, but it has nothing to do with the material. D wrong, because the price of gold is higher than that of silver, which means that the social labor productivity of producing gold is lower than that of producing silver.

Comments: This test requires students to master the meaning of goods. Commodities are products of labor used for exchange. The two basic attributes of commodities are use value and value. The difficulty of this question is low, and students are required to analyze and judge the materials on the basis of mastering book knowledge.