①统一后以圆形方孔“半两钱”通行天下
②奠定了此后2000多年中国铜钱的基本形状
③有利于维护国家的统一
④有利于各地经济的交流和发展
A:①②③④
B:②③④
C:①②④
D:①②③
______ Mary ______ John has been to China before, but they know a lot about it.
—I usually share them my classmates and talk about the stories each other.