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❓ 题目 According to the passage, why is the economic valuation of ecosystem services problematic?

A. Because most ecosystem services are too complex to be quantified in monetary terms.
B. Because many of these services are public goods and lack market prices, making valuation difficult.
C. Because ecologists oppose the idea of assigning monetary worth to nature.
D. Because the Millennium Ecosystem Assessment has already provided a complete valuation.

Because many of these services are public goods and lack market prices, making valuation difficult.