听力原文: The Old Canada Road is a long lost trail between the Canadian province of Quebec and Maine in the northeast corner of the United States. Yes it really was lost and finding it again was a complex process that involved state of our technology: how the location of the roads was pinpointed was very interesting. And I'll return to it as soon as I gave you a little background information. The road was begun in 1817, a few years before Maine even became a state. At the time Quebec was a major market for livestock, crops and fish. So a road to Quebec was seen by officials in Maine as necessary for trade. For about 20 years the movement of people and goods was mostly from Maine to Quebec, and then the trend reversed as thousands of Canadians immigrated to Maine to escape poor crops, the lack of jobs and the threat of disease. I think it was a color epidemic. Besides its negative reasons major building projects in Maine also made the state very attractive for the Canadians who needed work. I should stress though that immigration during that period went in both directions. In fact the flow of people and goods went completely unhindered. There wasn't even a border post until around 1850. The people of the time saw Maine and Quebec as a single region mainly because of the strong French influence which is still evident in Maine today. Eventually the road fell into disuse as a major railway was completed. Finally people simply forgot about it and that's how it came to be lost. This brings me back to the original topic.准时制库存是维持系统完整运行所需的最小库存。()下列协议中不是电子邮件协议的是。