单选题 The tone of the author of the passage in describing theories of co-evolution can best be described as one of

• (A) appreciation of the theory's ability to explain the disappearance of certain carbohydrate-rich plant species
• (B) admiration for the theory's refutation of the seed-disbursal theory of the disappearance of the carbohydrate-rich plant species
• (C) skepticism toward the theory's ability to account for the evolution of trade relations between agriculturalists and foragers
• (D) annoyance at the theory's failure to account for such phenomenon as the success of the sago palm
• (E) concern that the theory may be insufficient to discredit the Headland Hypothesis