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❓ 题目 According to the passage, why are ecosystem services often degraded?

A. A) They are too complex to be studied by economists.
B. B) They are public goods without clear property rights, leading to undervaluation.
C. C) They primarily provide cultural benefits that are not tangible.
D. D) They have already been fully valued in the economic market.

B) They are public goods without clear property rights, leading to undervaluation.