A summary of the actions of the many aggressive regimes in Europe of the past several centuries would include mostly religious "holy" wars and a desire for territorial expansion.
The County unit system. See the link below that will take you to that.
Answer: Most likely the industrial revolution.
Explanation: The use of machines in production became more and more prevalent, eventually many factories were built in cities which caused pollution therefore making the air gross.
It was the "League of Nations" that was the international governmental organization that the United States declined to join after World War I, since most Americans thought this would entangle them in more European wars.
Radiocarbon dating is the method of dating bone that would yield the most accurate results. This kind of dating technique is used for determining the age of any object that contains organic materials in it. This is the method that was developed by a person named Willard Libby in the late 1940s. Libby got the Nobel Prize in the year 1960 for his great work.