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Test analysis: this question examines commodity exchange. 1 wrong point of view. Skill exchange belongs to barter exchange, not commodity circulation. Skills in skill exchange are commodities, so they are the unity of use value and value. Skill exchange belongs to commodity exchange and should conform to the principle of equivalent exchange, so ② ③ is correct. The purpose of skill exchange is to gain use value, not value, so the answer should be B.

Comments: The key to this problem lies in the understanding of commodity circulation and barter. Commodity circulation: commodity exchange with money as the medium. Formula: W-G-W, barter is W-W, and there is no currency as a medium. Pay attention to distinguish between the two, this question is generally difficult.