One of the most （） challenges that the United States-and indeed, the world-will face in the next few decades is how to alleviate the growing stress that human activities are placing on the environment.

A．consequential

B．subsequent

C．emergent

D．pressing

70公里以下运价里程的动车组不进行任何形式（），一律执按公布票价执行。

A.打折优惠

B.折扣票价

C.市场调节

D.价格调整