What appears to be one criterion that scientist use when defining the timing of geological periods?

gold discovery in california, and pioneer settlers were sometimes pulled west because they wanted to make a better living. others received letters from friends or family members who had moved west. these letters often told about a good life on the frontier. the biggest factor that pulled pioneers west was the opportunity to buy land.

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answer; /// i believe that the correct answer is that it lets you see and evaluate different formats as you develop your workbook;