The completion of transcontinental railroads in the United States and Canada
<h2>~<u>Answer</u> :-</h2>
- An attack by one country against another over a border dispute.

What happened after the collapse of the Ming Dynasty were:
1) there were natural disasters, war and rebellions.
2) earthquakes.
3) war against the Japanese.
4) unusually dry and cold weather.
5) plague
6) misrule
7) money crisis
8) rebellion from Li Zicheng's troops.
The greatest common factor is 10. It is the biggest number that goes into 20 and 30 evenly.
~Silver