<span>C: adhering to the traditional values of the time period
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The idea of manifest destiny was the belief that people were destined for expansion across Northern America.
Polygamy is having more than one wife or husband at once, and anarchism is the rejection of the state or any other type of authority when organizing human societies.
Both types of behaviour are frowned upon by our society, to the point that they can be considered taboo. A taboo is an implicit (although sometimes it can be explicit, like through the enactment of a law) prohibition of something, because it is believed that the act goes against the agreed cultural or religious beliefs of a community. Establishing those kind of limits helps communities to be more organized and to have a stronger sense of "belonging." On the other hand, it can isolate those who think differently and cause the community to be closed to new ideas.
It was trench warfare that was used to a great extent in World War I. This led to a significant elongation of the conflict, since targeting soldiers was much harder.
