【单选题】听力原文: W: I finished the stories about Columbus last time. Now I would like to give you some details about the most truly American national holiday in the United States. M: Is it Christmas? W: No. Chri...
【简答题】In forestry, market failures that could exist ( but are not necessarily widespread ) include poorly ______, ______, ______, ______, unpriced negative and positive side effects, and outputs not easily ...