That would be survey research.
Surveys are used for the political polls as they are very good and appropriate for this kind of research as they consist of questions that have the aim of eliciting the specific information and data from the people about a particular subject. Surveys can take a wide variety of forms be that a simple phone interview or a kind of online survey.
Answer:
Predators
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Native Americans have been hunterers and gatherers up to the period when growing crops became available to them/when they discovered growing crops is a thing that could be done. The reason for this is that when you've started growing crops, you can safely stay on one spot and have a sufficient supply of food for a longer time period - this wasn't available before. However, even with the coming of agriculture, the still hunted and gathered as it was an important aspect of their life.
It was used to protect Athens from attacks :)
